{"id":1621,"date":"2020-06-26T16:33:46","date_gmt":"2020-06-26T20:33:46","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/chbe220\/?post_type=chapter&#038;p=1621"},"modified":"2020-08-12T14:49:38","modified_gmt":"2020-08-12T18:49:38","slug":"process-control","status":"publish","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/chbe220\/chapter\/process-control\/","title":{"raw":"Process Control","rendered":"Process Control"},"content":{"raw":"<div class=\"cell border-box-sizing text_cell rendered\">\r\n<div class=\"prompt input_prompt\"><\/div>\r\n<\/div>\r\n<div class=\"cell border-box-sizing text_cell rendered\">\r\n<div class=\"inner_cell\">\r\n<div class=\"text_cell_render border-box-sizing rendered_html\">\r\n<div class=\"textbox textbox--learning-objectives\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\">Learning Objectives<\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n<div class=\"cell border-box-sizing text_cell rendered\">\r\n<div class=\"inner_cell\">\r\n<div class=\"text_cell_render border-box-sizing rendered_html\">\r\n\r\nBy the end of this section, you should be able to:\r\n\r\n<strong>Apply<\/strong> control strategies to control common process variables: flow, liquid pressure, liquid level, and temperature of endothermic process streams.\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div class=\"cell border-box-sizing text_cell rendered\">\r\n<div class=\"prompt input_prompt\"><\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n&nbsp;\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div class=\"cell border-box-sizing text_cell rendered\">\r\n<div class=\"inner_cell\">\r\n<div class=\"text_cell_render border-box-sizing rendered_html\">\r\n<h2>Control System Elements<\/h2>\r\nSome common terms used in process control:\r\n<ul>\r\n \t<li><strong>Set-Point<\/strong>: this is a target or desired value of a variable in the system (such as flowrate, temperature, etc.)<\/li>\r\n \t<li><strong>Disturbance Variable<\/strong>: a variable that we have no control over in the process but affects the material or heat flow of the process.<\/li>\r\n \t<li><strong>Manipulated Variable<\/strong>: a variable that we can control in the process and directly affects the output of the process.<\/li>\r\n \t<li><strong>Process Variable<\/strong>: the variable in the system or process that we desire to control.<\/li>\r\n \t<li><strong>Controlled Variable<\/strong>: the output process variable we compare to the set-point.<\/li>\r\n<\/ul>\r\n<img class=\" wp-image-1234 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/ProcessControl-300x169.png\" alt=\"\" width=\"604\" height=\"340\" \/>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div class=\"cell border-box-sizing text_cell rendered\">\r\n<div class=\"prompt input_prompt\"><\/div>\r\n<div class=\"inner_cell\">\r\n<div class=\"text_cell_render border-box-sizing rendered_html\">\r\n<div class=\"textbox textbox--exercises\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\">Exercise: Control System Variables<\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n<div class=\"cell border-box-sizing text_cell rendered\">\r\n<div class=\"inner_cell\">\r\n<div class=\"text_cell_render border-box-sizing rendered_html\">\r\n<div>\r\n\r\nYou are driving a car and are approaching a hill. Assume there are three variables in this system:\r\n<ol>\r\n \t<li>gas pedal<\/li>\r\n \t<li>the hill<\/li>\r\n \t<li>the car's speed<\/li>\r\n<\/ol>\r\nClassify each of these variables as process\/controlled variable, manipulated variable, or disturbance variable.\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div class=\"cell border-box-sizing text_cell rendered\">\r\n<div class=\"prompt input_prompt\"><\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div class=\"textbox\">\r\n<h3>Solution<\/h3>\r\nThe gas pedal will be the manipulated variable since you have direct control on the gas pedal. The hill will be the disturbance variable, because you cannot control the hill's steepness and how this will affect the system. Finally, the car's speed is the process or controlled variable, since it is the system's output variable.\r\n\r\n<\/div>\r\n&nbsp;\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div class=\"cell border-box-sizing text_cell rendered\">\r\n<div class=\"inner_cell\">\r\n<div class=\"text_cell_render border-box-sizing rendered_html\">\r\n<h3>Flow Measurement<\/h3>\r\n<blockquote><strong>1 - Obstruction Meter<\/strong>\r\n\r\n<img class=\" wp-image-1232 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/ObstructionMeter-300x150.png\" alt=\"\" width=\"534\" height=\"267\" \/>\r\n\r\nAn obstruction meter measures the change in pressure $\\Delta P$ and correlates it to flow.\r\n\r\n<strong>2 - Rotational or Turbine Flowmeter <\/strong>\r\n\r\n<img class=\" wp-image-1239 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/TurbineMeter-300x130.png\" alt=\"\" width=\"494\" height=\"214\" \/>\r\n\r\nA rotational or turbine flowmeter measures the speed of the rotation of the turbine and correlates it to flow.<\/blockquote>\r\n<img class=\" wp-image-1243 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/FlowControl-300x140.png\" alt=\"\" width=\"519\" height=\"242\" \/>\r\n\r\nFor the flow control loop depicted above:\r\n<ul>\r\n \t<li>If the flow is too low \u2192 open the valve<\/li>\r\n \t<li>If the flow is too high \u2192 close the valve<\/li>\r\n<\/ul>\r\nThe transmitter is generally placed sufficiently upstream of the valve so that the flow reading is typically not affected by the valve.\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div class=\"cell border-box-sizing text_cell rendered\">\r\n<div class=\"prompt input_prompt\"><\/div>\r\n<div class=\"inner_cell\">\r\n<div class=\"text_cell_render border-box-sizing rendered_html\">\r\n<h3>Level Measurement<\/h3>\r\nMany level measurement devices are available (pressure, weight, thermal), but float and sonic\/radar level measures are the most common.\r\n<blockquote><strong>1 - Float<\/strong>\r\n\r\n<img class=\" wp-image-1242 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Float-300x175.png\" alt=\"\" width=\"542\" height=\"316\" \/>\r\n\r\n&nbsp;\r\n\r\n<strong>2 - Sonic\/Radar <\/strong>\r\n\r\n<img class=\" wp-image-1236 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Sonic-300x206.png\" alt=\"\" width=\"446\" height=\"306\" \/>\r\n\r\nA sonic or radar device measures the level of the tank by measuring the time for wave to reach the liquid-gas interphase and reflect back to the device, and correlating the time to distance. The sonic or radar device can be installed from the top or bottom of the tank.<\/blockquote>\r\nA typical level control loop is depicted:\r\n\r\n<img class=\" wp-image-1230 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/LevelControl-300x129.png\" alt=\"\" width=\"537\" height=\"231\" \/>\r\n\r\nFor the level control loop depicted above:\r\n<ul>\r\n \t<li>If the level is too low \u2192 close the valve below the tank (outlet valve)<\/li>\r\n \t<li>If the level is too high \u2192 open the valve below the tank (outlet valve)<\/li>\r\n<\/ul>\r\nNote that we could also manipulate the inlet valve to affect the tank level, but typically in these systems, the outlet valve is used to control the level. We will stick with this convention in this class.\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div class=\"cell border-box-sizing text_cell rendered\">\r\n<div class=\"prompt input_prompt\"><\/div>\r\n<div class=\"inner_cell\">\r\n<div class=\"text_cell_render border-box-sizing rendered_html\">\r\n<h3>Pressure Measurement<\/h3>\r\n<blockquote><strong>1 - Manometer<\/strong>\r\n\r\n<img class=\" wp-image-1231 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Manometer-269x300.png\" alt=\"\" width=\"349\" height=\"389\" \/>\r\n\r\nManometers measure difference in fluid height and correlate it to pressure.\r\n\r\n<strong>2 - Differential Pressure Cells <\/strong>\r\n\r\n<img class=\" wp-image-1241 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Diaphragm-300x120.png\" alt=\"\" width=\"503\" height=\"201\" \/>\r\n\r\nA differential pressure cell measures the deflection of the membrane and correlates it to change in pressure $\\Delta P$.<\/blockquote>\r\nA typical liquid pressure control loop is depicted:\r\n\r\n<img class=\" wp-image-1233 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/PressureControl-300x163.png\" alt=\"\" width=\"473\" height=\"258\" \/>\r\n\r\nFor the level control loop depicted above:\r\n<ul>\r\n \t<li>If the pressure is too low \u2192 open the valve<\/li>\r\n \t<li>If the pressure is too high \u2192 close the valve<\/li>\r\n<\/ul>\r\nFor a centrifugal pump (least expensive and most common for liquids), the line can be closed without immediate damage to the pump. Other pumps (positive displacement pumps) will use other strategies.\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div class=\"cell border-box-sizing text_cell rendered\">\r\n<div class=\"prompt input_prompt\"><\/div>\r\n<div class=\"inner_cell\">\r\n<div class=\"text_cell_render border-box-sizing rendered_html\">\r\n<h3>Temperature Measurement<\/h3>\r\n<blockquote><strong>1 - Expansion-based<\/strong>\r\n\r\n<img class=\" wp-image-1238 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Thermometer-156x300.png\" alt=\"\" width=\"210\" height=\"404\" \/>\r\n<p style=\"text-align: center\">Image from <a title=\"via Wikimedia Commons\" href=\"https:\/\/commons.wikimedia.org\/wiki\/File:Thermometer_(PSF).png\">Pearson Scott Foresman<\/a> \/ Public domain<\/p>\r\nExpansion-based thermometers measure fluid expansion and correlate it to temperature.\r\n\r\n<strong>2 - Electrical <\/strong>\r\n<p style=\"text-align: center\"><img class=\"wp-image-1237 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Thermocouple-300x94.png\" alt=\"\" width=\"517\" height=\"162\" \/>Image from <a title=\"via Wikimedia Commons\" href=\"https:\/\/commons.wikimedia.org\/wiki\/File:Thermocouple_circuit_Ktype_including_voltmeter_temperature.svg\">Nanite<\/a> \/ CC0<\/p>\r\nThermocouples or resistance temperature devices measure changes in electrical properties and correlate them to temperature. Electrical temperature measurements are the most commonly used inplants as switching combination of metals can adopt to a wide range on temperature.<\/blockquote>\r\nA typical slow-response endothermic temperature control loop is depicted:\r\n\r\n<img class=\" wp-image-1235 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/SlowResponseControl-300x133.png\" alt=\"\" width=\"552\" height=\"245\" \/>\r\n\r\nFor the temperature control loop depicted above:\r\n<ul>\r\n \t<li>if the temperature (T<sub>2<\/sub>) is too high \u2192 close the valve, because it allows more condensate to be stored in the heat exchanger, therefore allow less steam in the heat exchanger and lower the amount of heat released by condensation of steam<\/li>\r\n \t<li>if the temperature (T<sub>2<\/sub>) is too low \u2192 open the valve<\/li>\r\n<\/ul>\r\n<blockquote>A slow-response endothermic temperature control loop is classified as <strong>slow<\/strong> because it takes a longer time to see a temperature change. The response of the system is dependant on the amount of steam that condenses in the heat exchanger. When the outflow of condensate is manipulated, the vapour-liquid equilibrium point is shifted, which affects the rate of condensation\/vaporization. The equilibrium shift speed causes a delay in the response time of temperature control.<\/blockquote>\r\nA typical critical endothermic temperature control loop is depicted:\r\n\r\n<img class=\" wp-image-1240 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/CriticalControl-300x119.png\" alt=\"\" width=\"595\" height=\"236\" \/>\r\n\r\nFor the temperature control loop depicted above:\r\n<ul>\r\n \t<li>if the temperature (T<sub>2<\/sub>) is too high \u2192 open the valve, because it allows the bypass of the process fluid that does not go through the heat exchanger to mix with the outlet process fluid<\/li>\r\n \t<li>if the temperature (T<sub>2<\/sub>) is too low \u2192 close the valve<\/li>\r\n<\/ul>\r\n<blockquote>A critical endothermic temperature control loop is <strong>faster<\/strong> than a slow-response endothermic control loop because the temperature of the process fluid is directly changed. This eliminates the lag that would be present from manipulating the steam temperature.<\/blockquote>\r\n<div>\r\n<div class=\"textbox textbox--examples\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\">Example: Endothermic Temperature Control Loops<\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n\r\nConsider a heat exchanger where an endothermic temperature control loop is present in the system (which means the process stream absorbs heat from the utilities). There is a [latex]5^{\\circ}C[\/latex]\u00a0(from the set-point) increase in the outlet temperature of the process fluid. Which endothermic control loop will decrease the temperature back to its original set-point faster and why?\r\n\r\nFor a <strong> slow-response endothermic temperature control loop <\/strong>:\r\n<blockquote>When the temperature change is detected, the controller will close the valve slightly to allow for less condensate to flow out of the heat exchanger. This will allow less steam in the heat exchanger to provide heat through condensation, and eventually cause the outlet process fluid temperature to decrease to the set-point temperature<\/blockquote>\r\nFor a <strong> critical endothermic temperature control loop <\/strong>:\r\n<blockquote>When the temperature change is detected, the controller will open the valve of the cold process fluid. This will directly add cold process fluid to the outlet process fluid and directly decrease the temperature back to its set-point, without any delay.<\/blockquote>\r\nTherefore, a critical endothermic temperature control loop is going to decrease the temperature back to its original set-point faster.\r\n\r\n<\/div>\r\n<\/div>\r\n&nbsp;\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<div class=\"cell border-box-sizing text_cell rendered\">\r\n<div class=\"prompt input_prompt\"><\/div>\r\n<div class=\"inner_cell\">\r\n<div class=\"text_cell_render border-box-sizing rendered_html\">\r\n<div>\r\n<div class=\"textbox textbox--exercises\"><header class=\"textbox__header\">\r\n<p class=\"textbox__title\">Exercise: Heat Exchanger Control<\/p>\r\n\r\n<\/header>\r\n<div class=\"textbox__content\">\r\n\r\nConsider the following heat exchanger system. We'd like to control the outlet cold temperature [latex]T_{C,out}[\/latex].\r\n\r\n<img class=\" wp-image-1244 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/HX.png-300x157.png\" alt=\"\" width=\"529\" height=\"277\" \/>\r\n\r\nSuggest 2 different control loops that we can implement to this system.\r\n\r\n<\/div>\r\n<\/div>\r\n<div class=\"textbox\">\r\n<h3>Solution<\/h3>\r\nThe first control strategy measures the process variable ([latex]T_{C,out}[\/latex]) and adjusts the outlet hot stream's temperature ([latex]T_{H,out}[\/latex]) by manipulating the outlet flowrate of the hot fluid. This control strategy is known as the slow-response endothermic control loop.\r\n\r\n<img class=\" wp-image-1245 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/HX1-300x160.png\" alt=\"\" width=\"534\" height=\"285\" \/>\r\n\r\nThe second control strategy measures the process variable ([latex]T_{C,out}[\/latex]) and adjusts the inlet cold stream's temperature ([latex]T_{C,in}[\/latex]) by adding more cold process fluid to the outlet cold stream. This control strategy is known as the critical endothermic control loop.\r\n\r\n<img class=\" wp-image-1229 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/HX2-300x165.png\" alt=\"\" width=\"535\" height=\"294\" \/>\r\n\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>\r\n<\/div>","rendered":"<div class=\"cell border-box-sizing text_cell rendered\">\n<div class=\"prompt input_prompt\"><\/div>\n<\/div>\n<div class=\"cell border-box-sizing text_cell rendered\">\n<div class=\"inner_cell\">\n<div class=\"text_cell_render border-box-sizing rendered_html\">\n<div class=\"textbox textbox--learning-objectives\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Learning Objectives<\/p>\n<\/header>\n<div class=\"textbox__content\">\n<div class=\"cell border-box-sizing text_cell rendered\">\n<div class=\"inner_cell\">\n<div class=\"text_cell_render border-box-sizing rendered_html\">\n<p>By the end of this section, you should be able to:<\/p>\n<p><strong>Apply<\/strong> control strategies to control common process variables: flow, liquid pressure, liquid level, and temperature of endothermic process streams.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<div class=\"cell border-box-sizing text_cell rendered\">\n<div class=\"prompt input_prompt\"><\/div>\n<\/div>\n<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<\/div>\n<\/div>\n<\/div>\n<div class=\"cell border-box-sizing text_cell rendered\">\n<div class=\"inner_cell\">\n<div class=\"text_cell_render border-box-sizing rendered_html\">\n<h2>Control System Elements<\/h2>\n<p>Some common terms used in process control:<\/p>\n<ul>\n<li><strong>Set-Point<\/strong>: this is a target or desired value of a variable in the system (such as flowrate, temperature, etc.)<\/li>\n<li><strong>Disturbance Variable<\/strong>: a variable that we have no control over in the process but affects the material or heat flow of the process.<\/li>\n<li><strong>Manipulated Variable<\/strong>: a variable that we can control in the process and directly affects the output of the process.<\/li>\n<li><strong>Process Variable<\/strong>: the variable in the system or process that we desire to control.<\/li>\n<li><strong>Controlled Variable<\/strong>: the output process variable we compare to the set-point.<\/li>\n<\/ul>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-1234 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/ProcessControl-300x169.png\" alt=\"\" width=\"604\" height=\"340\" srcset=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/ProcessControl-300x169.png 300w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/ProcessControl-1024x577.png 1024w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/ProcessControl-768x433.png 768w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/ProcessControl-65x37.png 65w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/ProcessControl-225x127.png 225w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/ProcessControl-350x197.png 350w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/ProcessControl.png 1041w\" sizes=\"auto, (max-width: 604px) 100vw, 604px\" \/><\/p>\n<\/div>\n<\/div>\n<\/div>\n<div class=\"cell border-box-sizing text_cell rendered\">\n<div class=\"prompt input_prompt\"><\/div>\n<div class=\"inner_cell\">\n<div class=\"text_cell_render border-box-sizing rendered_html\">\n<div class=\"textbox textbox--exercises\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Exercise: Control System Variables<\/p>\n<\/header>\n<div class=\"textbox__content\">\n<div class=\"cell border-box-sizing text_cell rendered\">\n<div class=\"inner_cell\">\n<div class=\"text_cell_render border-box-sizing rendered_html\">\n<div>\n<p>You are driving a car and are approaching a hill. Assume there are three variables in this system:<\/p>\n<ol>\n<li>gas pedal<\/li>\n<li>the hill<\/li>\n<li>the car&#8217;s speed<\/li>\n<\/ol>\n<p>Classify each of these variables as process\/controlled variable, manipulated variable, or disturbance variable.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div class=\"cell border-box-sizing text_cell rendered\">\n<div class=\"prompt input_prompt\"><\/div>\n<\/div>\n<\/div>\n<\/div>\n<div class=\"textbox\">\n<h3>Solution<\/h3>\n<p>The gas pedal will be the manipulated variable since you have direct control on the gas pedal. The hill will be the disturbance variable, because you cannot control the hill&#8217;s steepness and how this will affect the system. Finally, the car&#8217;s speed is the process or controlled variable, since it is the system&#8217;s output variable.<\/p>\n<\/div>\n<p>&nbsp;<\/p>\n<\/div>\n<\/div>\n<\/div>\n<div class=\"cell border-box-sizing text_cell rendered\">\n<div class=\"inner_cell\">\n<div class=\"text_cell_render border-box-sizing rendered_html\">\n<h3>Flow Measurement<\/h3>\n<blockquote><p><strong>1 &#8211; Obstruction Meter<\/strong><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-1232 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/ObstructionMeter-300x150.png\" alt=\"\" width=\"534\" height=\"267\" srcset=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/ObstructionMeter-300x150.png 300w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/ObstructionMeter-65x33.png 65w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/ObstructionMeter-225x113.png 225w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/ObstructionMeter-350x175.png 350w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/ObstructionMeter.png 710w\" sizes=\"auto, (max-width: 534px) 100vw, 534px\" \/><\/p>\n<p>An obstruction meter measures the change in pressure $\\Delta P$ and correlates it to flow.<\/p>\n<p><strong>2 &#8211; Rotational or Turbine Flowmeter <\/strong><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-1239 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/TurbineMeter-300x130.png\" alt=\"\" width=\"494\" height=\"214\" srcset=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/TurbineMeter-300x130.png 300w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/TurbineMeter-768x334.png 768w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/TurbineMeter-65x28.png 65w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/TurbineMeter-225x98.png 225w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/TurbineMeter-350x152.png 350w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/TurbineMeter.png 845w\" sizes=\"auto, (max-width: 494px) 100vw, 494px\" \/><\/p>\n<p>A rotational or turbine flowmeter measures the speed of the rotation of the turbine and correlates it to flow.<\/p><\/blockquote>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-1243 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/FlowControl-300x140.png\" alt=\"\" width=\"519\" height=\"242\" srcset=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/FlowControl-300x140.png 300w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/FlowControl-1024x479.png 1024w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/FlowControl-768x359.png 768w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/FlowControl-65x30.png 65w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/FlowControl-225x105.png 225w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/FlowControl-350x164.png 350w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/FlowControl.png 1093w\" sizes=\"auto, (max-width: 519px) 100vw, 519px\" \/><\/p>\n<p>For the flow control loop depicted above:<\/p>\n<ul>\n<li>If the flow is too low \u2192 open the valve<\/li>\n<li>If the flow is too high \u2192 close the valve<\/li>\n<\/ul>\n<p>The transmitter is generally placed sufficiently upstream of the valve so that the flow reading is typically not affected by the valve.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<div class=\"cell border-box-sizing text_cell rendered\">\n<div class=\"prompt input_prompt\"><\/div>\n<div class=\"inner_cell\">\n<div class=\"text_cell_render border-box-sizing rendered_html\">\n<h3>Level Measurement<\/h3>\n<p>Many level measurement devices are available (pressure, weight, thermal), but float and sonic\/radar level measures are the most common.<\/p>\n<blockquote><p><strong>1 &#8211; Float<\/strong><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-1242 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Float-300x175.png\" alt=\"\" width=\"542\" height=\"316\" srcset=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Float-300x175.png 300w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Float-768x448.png 768w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Float-65x38.png 65w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Float-225x131.png 225w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Float-350x204.png 350w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Float.png 905w\" sizes=\"auto, (max-width: 542px) 100vw, 542px\" \/><\/p>\n<p>&nbsp;<\/p>\n<p><strong>2 &#8211; Sonic\/Radar <\/strong><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-1236 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Sonic-300x206.png\" alt=\"\" width=\"446\" height=\"306\" srcset=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Sonic-300x206.png 300w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Sonic-65x45.png 65w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Sonic-225x154.png 225w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Sonic-350x240.png 350w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Sonic.png 749w\" sizes=\"auto, (max-width: 446px) 100vw, 446px\" \/><\/p>\n<p>A sonic or radar device measures the level of the tank by measuring the time for wave to reach the liquid-gas interphase and reflect back to the device, and correlating the time to distance. The sonic or radar device can be installed from the top or bottom of the tank.<\/p><\/blockquote>\n<p>A typical level control loop is depicted:<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-1230 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/LevelControl-300x129.png\" alt=\"\" width=\"537\" height=\"231\" srcset=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/LevelControl-300x129.png 300w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/LevelControl-1024x441.png 1024w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/LevelControl-768x331.png 768w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/LevelControl-65x28.png 65w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/LevelControl-225x97.png 225w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/LevelControl-350x151.png 350w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/LevelControl.png 1303w\" sizes=\"auto, (max-width: 537px) 100vw, 537px\" \/><\/p>\n<p>For the level control loop depicted above:<\/p>\n<ul>\n<li>If the level is too low \u2192 close the valve below the tank (outlet valve)<\/li>\n<li>If the level is too high \u2192 open the valve below the tank (outlet valve)<\/li>\n<\/ul>\n<p>Note that we could also manipulate the inlet valve to affect the tank level, but typically in these systems, the outlet valve is used to control the level. We will stick with this convention in this class.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<div class=\"cell border-box-sizing text_cell rendered\">\n<div class=\"prompt input_prompt\"><\/div>\n<div class=\"inner_cell\">\n<div class=\"text_cell_render border-box-sizing rendered_html\">\n<h3>Pressure Measurement<\/h3>\n<blockquote><p><strong>1 &#8211; Manometer<\/strong><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-1231 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Manometer-269x300.png\" alt=\"\" width=\"349\" height=\"389\" srcset=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Manometer-269x300.png 269w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Manometer-65x73.png 65w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Manometer-225x251.png 225w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Manometer-350x391.png 350w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Manometer.png 452w\" sizes=\"auto, (max-width: 349px) 100vw, 349px\" \/><\/p>\n<p>Manometers measure difference in fluid height and correlate it to pressure.<\/p>\n<p><strong>2 &#8211; Differential Pressure Cells <\/strong><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-1241 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Diaphragm-300x120.png\" alt=\"\" width=\"503\" height=\"201\" srcset=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Diaphragm-300x120.png 300w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Diaphragm-1024x408.png 1024w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Diaphragm-768x306.png 768w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Diaphragm-65x26.png 65w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Diaphragm-225x90.png 225w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Diaphragm-350x140.png 350w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Diaphragm.png 1236w\" sizes=\"auto, (max-width: 503px) 100vw, 503px\" \/><\/p>\n<p>A differential pressure cell measures the deflection of the membrane and correlates it to change in pressure $\\Delta P$.<\/p><\/blockquote>\n<p>A typical liquid pressure control loop is depicted:<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-1233 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/PressureControl-300x163.png\" alt=\"\" width=\"473\" height=\"258\" srcset=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/PressureControl-300x163.png 300w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/PressureControl-768x418.png 768w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/PressureControl-65x35.png 65w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/PressureControl-225x123.png 225w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/PressureControl-350x191.png 350w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/PressureControl.png 999w\" sizes=\"auto, (max-width: 473px) 100vw, 473px\" \/><\/p>\n<p>For the level control loop depicted above:<\/p>\n<ul>\n<li>If the pressure is too low \u2192 open the valve<\/li>\n<li>If the pressure is too high \u2192 close the valve<\/li>\n<\/ul>\n<p>For a centrifugal pump (least expensive and most common for liquids), the line can be closed without immediate damage to the pump. Other pumps (positive displacement pumps) will use other strategies.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<div class=\"cell border-box-sizing text_cell rendered\">\n<div class=\"prompt input_prompt\"><\/div>\n<div class=\"inner_cell\">\n<div class=\"text_cell_render border-box-sizing rendered_html\">\n<h3>Temperature Measurement<\/h3>\n<blockquote><p><strong>1 &#8211; Expansion-based<\/strong><\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-1238 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Thermometer-156x300.png\" alt=\"\" width=\"210\" height=\"404\" srcset=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Thermometer-156x300.png 156w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Thermometer-533x1024.png 533w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Thermometer-768x1477.png 768w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Thermometer-799x1536.png 799w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Thermometer-1065x2048.png 1065w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Thermometer-65x125.png 65w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Thermometer-225x433.png 225w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Thermometer-350x673.png 350w\" sizes=\"auto, (max-width: 210px) 100vw, 210px\" \/><\/p>\n<p style=\"text-align: center\">Image from <a title=\"via Wikimedia Commons\" href=\"https:\/\/commons.wikimedia.org\/wiki\/File:Thermometer_(PSF).png\">Pearson Scott Foresman<\/a> \/ Public domain<\/p>\n<p>Expansion-based thermometers measure fluid expansion and correlate it to temperature.<\/p>\n<p><strong>2 &#8211; Electrical <\/strong><\/p>\n<p style=\"text-align: center\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-1237 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Thermocouple-300x94.png\" alt=\"\" width=\"517\" height=\"162\" srcset=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Thermocouple-300x94.png 300w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Thermocouple-1024x321.png 1024w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Thermocouple-768x240.png 768w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Thermocouple-1536x481.png 1536w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Thermocouple-65x20.png 65w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Thermocouple-225x70.png 225w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Thermocouple-350x110.png 350w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/Thermocouple.png 1581w\" sizes=\"auto, (max-width: 517px) 100vw, 517px\" \/>Image from <a title=\"via Wikimedia Commons\" href=\"https:\/\/commons.wikimedia.org\/wiki\/File:Thermocouple_circuit_Ktype_including_voltmeter_temperature.svg\">Nanite<\/a> \/ CC0<\/p>\n<p>Thermocouples or resistance temperature devices measure changes in electrical properties and correlate them to temperature. Electrical temperature measurements are the most commonly used inplants as switching combination of metals can adopt to a wide range on temperature.<\/p><\/blockquote>\n<p>A typical slow-response endothermic temperature control loop is depicted:<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-1235 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/SlowResponseControl-300x133.png\" alt=\"\" width=\"552\" height=\"245\" srcset=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/SlowResponseControl-300x133.png 300w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/SlowResponseControl-1024x455.png 1024w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/SlowResponseControl-768x341.png 768w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/SlowResponseControl-65x29.png 65w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/SlowResponseControl-225x100.png 225w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/SlowResponseControl-350x156.png 350w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/SlowResponseControl.png 1107w\" sizes=\"auto, (max-width: 552px) 100vw, 552px\" \/><\/p>\n<p>For the temperature control loop depicted above:<\/p>\n<ul>\n<li>if the temperature (T<sub>2<\/sub>) is too high \u2192 close the valve, because it allows more condensate to be stored in the heat exchanger, therefore allow less steam in the heat exchanger and lower the amount of heat released by condensation of steam<\/li>\n<li>if the temperature (T<sub>2<\/sub>) is too low \u2192 open the valve<\/li>\n<\/ul>\n<blockquote><p>A slow-response endothermic temperature control loop is classified as <strong>slow<\/strong> because it takes a longer time to see a temperature change. The response of the system is dependant on the amount of steam that condenses in the heat exchanger. When the outflow of condensate is manipulated, the vapour-liquid equilibrium point is shifted, which affects the rate of condensation\/vaporization. The equilibrium shift speed causes a delay in the response time of temperature control.<\/p><\/blockquote>\n<p>A typical critical endothermic temperature control loop is depicted:<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-1240 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/CriticalControl-300x119.png\" alt=\"\" width=\"595\" height=\"236\" srcset=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/CriticalControl-300x119.png 300w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/CriticalControl-1024x407.png 1024w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/CriticalControl-768x305.png 768w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/CriticalControl-65x26.png 65w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/CriticalControl-225x89.png 225w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/CriticalControl-350x139.png 350w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/CriticalControl.png 1115w\" sizes=\"auto, (max-width: 595px) 100vw, 595px\" \/><\/p>\n<p>For the temperature control loop depicted above:<\/p>\n<ul>\n<li>if the temperature (T<sub>2<\/sub>) is too high \u2192 open the valve, because it allows the bypass of the process fluid that does not go through the heat exchanger to mix with the outlet process fluid<\/li>\n<li>if the temperature (T<sub>2<\/sub>) is too low \u2192 close the valve<\/li>\n<\/ul>\n<blockquote><p>A critical endothermic temperature control loop is <strong>faster<\/strong> than a slow-response endothermic control loop because the temperature of the process fluid is directly changed. This eliminates the lag that would be present from manipulating the steam temperature.<\/p><\/blockquote>\n<div>\n<div class=\"textbox textbox--examples\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Example: Endothermic Temperature Control Loops<\/p>\n<\/header>\n<div class=\"textbox__content\">\n<p>Consider a heat exchanger where an endothermic temperature control loop is present in the system (which means the process stream absorbs heat from the utilities). There is a [latex]5^{\\circ}C[\/latex]\u00a0(from the set-point) increase in the outlet temperature of the process fluid. Which endothermic control loop will decrease the temperature back to its original set-point faster and why?<\/p>\n<p>For a <strong> slow-response endothermic temperature control loop <\/strong>:<\/p>\n<blockquote><p>When the temperature change is detected, the controller will close the valve slightly to allow for less condensate to flow out of the heat exchanger. This will allow less steam in the heat exchanger to provide heat through condensation, and eventually cause the outlet process fluid temperature to decrease to the set-point temperature<\/p><\/blockquote>\n<p>For a <strong> critical endothermic temperature control loop <\/strong>:<\/p>\n<blockquote><p>When the temperature change is detected, the controller will open the valve of the cold process fluid. This will directly add cold process fluid to the outlet process fluid and directly decrease the temperature back to its set-point, without any delay.<\/p><\/blockquote>\n<p>Therefore, a critical endothermic temperature control loop is going to decrease the temperature back to its original set-point faster.<\/p>\n<\/div>\n<\/div>\n<p>&nbsp;<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<div class=\"cell border-box-sizing text_cell rendered\">\n<div class=\"prompt input_prompt\"><\/div>\n<div class=\"inner_cell\">\n<div class=\"text_cell_render border-box-sizing rendered_html\">\n<div>\n<div class=\"textbox textbox--exercises\">\n<header class=\"textbox__header\">\n<p class=\"textbox__title\">Exercise: Heat Exchanger Control<\/p>\n<\/header>\n<div class=\"textbox__content\">\n<p>Consider the following heat exchanger system. We&#8217;d like to control the outlet cold temperature [latex]T_{C,out}[\/latex].<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-1244 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/HX.png-300x157.png\" alt=\"\" width=\"529\" height=\"277\" srcset=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/HX.png-300x157.png 300w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/HX.png-768x401.png 768w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/HX.png-65x34.png 65w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/HX.png-225x117.png 225w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/HX.png-350x183.png 350w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/HX.png.png 887w\" sizes=\"auto, (max-width: 529px) 100vw, 529px\" \/><\/p>\n<p>Suggest 2 different control loops that we can implement to this system.<\/p>\n<\/div>\n<\/div>\n<div class=\"textbox\">\n<h3>Solution<\/h3>\n<p>The first control strategy measures the process variable ([latex]T_{C,out}[\/latex]) and adjusts the outlet hot stream&#8217;s temperature ([latex]T_{H,out}[\/latex]) by manipulating the outlet flowrate of the hot fluid. This control strategy is known as the slow-response endothermic control loop.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-1245 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/HX1-300x160.png\" alt=\"\" width=\"534\" height=\"285\" srcset=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/HX1-300x160.png 300w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/HX1-1024x547.png 1024w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/HX1-768x410.png 768w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/HX1-65x35.png 65w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/HX1-225x120.png 225w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/HX1-350x187.png 350w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/HX1.png 1138w\" sizes=\"auto, (max-width: 534px) 100vw, 534px\" \/><\/p>\n<p>The second control strategy measures the process variable ([latex]T_{C,out}[\/latex]) and adjusts the inlet cold stream&#8217;s temperature ([latex]T_{C,in}[\/latex]) by adding more cold process fluid to the outlet cold stream. This control strategy is known as the critical endothermic control loop.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-1229 aligncenter\" src=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/HX2-300x165.png\" alt=\"\" width=\"535\" height=\"294\" srcset=\"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/HX2-300x165.png 300w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/HX2-1024x562.png 1024w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/HX2-768x421.png 768w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/HX2-65x36.png 65w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/HX2-225x123.png 225w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/HX2-350x192.png 350w, https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-content\/uploads\/sites\/1010\/2020\/06\/HX2.png 1125w\" sizes=\"auto, (max-width: 535px) 100vw, 535px\" \/><\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n","protected":false},"author":949,"menu_order":4,"comment_status":"closed","ping_status":"closed","template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":[],"pb_section_license":""},"chapter-type":[],"contributor":[],"license":[],"class_list":["post-1621","chapter","type-chapter","status-publish","hentry"],"part":1451,"_links":{"self":[{"href":"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-json\/pressbooks\/v2\/chapters\/1621","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-json\/wp\/v2\/users\/949"}],"replies":[{"embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-json\/wp\/v2\/comments?post=1621"}],"version-history":[{"count":7,"href":"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-json\/pressbooks\/v2\/chapters\/1621\/revisions"}],"predecessor-version":[{"id":2697,"href":"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-json\/pressbooks\/v2\/chapters\/1621\/revisions\/2697"}],"part":[{"href":"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-json\/pressbooks\/v2\/parts\/1451"}],"metadata":[{"href":"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-json\/pressbooks\/v2\/chapters\/1621\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-json\/wp\/v2\/media?parent=1621"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-json\/pressbooks\/v2\/chapter-type?post=1621"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-json\/wp\/v2\/contributor?post=1621"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.bccampus.ca\/chbe220\/wp-json\/wp\/v2\/license?post=1621"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}