{"id":232,"date":"2014-09-04T02:01:07","date_gmt":"2014-09-04T02:01:07","guid":{"rendered":"http:\/\/www.heatsinkcalculator.com\/blog\/?p=232"},"modified":"2016-01-31T04:08:37","modified_gmt":"2016-01-31T04:08:37","slug":"estimating-forced-convection-cooled-heat-sink-performance-in-a-ventilated-enclosure-part-2","status":"publish","type":"post","link":"https:\/\/www.heatsinkcalculator.com\/blog\/estimating-forced-convection-cooled-heat-sink-performance-in-a-ventilated-enclosure-part-2\/","title":{"rendered":"Estimating Forced Convection Cooled Heat Sink Performance in a Ventilated Enclosure (Part 2)"},"content":{"rendered":"<p>The <a href=\"http:\/\/www.heatsinkcalculator.com\" target=\"_blank\">HeatSinkCalculator<\/a> includes an option to input a fan curve of the fan used to cool the heat sink. This option can be exploited to allow the simulation of the heat sink and fan in a ventilated enclosure as was outlined in <a title=\"Estimating Forced Convection Cooled Heat Sink Performance in a Ventilated Enclosure (Part 1)\" href=\"http:\/\/www.heatsinkcalculator.com\/blog\/archives\/162\">part 1<\/a> of this article.<\/p>\n<p>It is assumed that the readers of this article already reviewed <a title=\"Estimating Forced Convection Cooled Heat Sink Performance in a Ventilated Enclosure (Part 1)\" href=\"http:\/\/www.heatsinkcalculator.com\/blog\/archives\/162\">part 1<\/a>. Recall from the previous article equation 1 that defines the total pressure difference around the flow network loop.<\/p>\n<p><img src='http:\/\/s.wordpress.com\/latex.php?latex=%5Cdisplaystyle%20%5CDelta%20P_%7Bvent1%7D%2B%5CDelta%20P_%7Bfan%7D%2B%5CDelta%20P_%7Bhs%7D%2B%5CDelta%20P_%7Bvent2%7D%3D0&bg=ffffff&fg=000000&s=0' alt='Latex formula' title='Latex formula' class='latex' \/>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 (1)<\/p>\n<p>The pressure differences across the fan and two ventilation openings can be summed to create a single parameter \u0394P<sub>fan<sup>*<\/sup><\/sub> that defines the total pressure difference across all three components.\u00a0 The parameter \u0394P<sub>fan<sup>*<\/sup><\/sub> represents the modified fan curve.\u00a0 This calculation is carried out at the specified volumetric flow rate of each point on the fan curve to generate the modified fan curve. Equation 1 is now reduced to equation 2. Please note that the pressure difference across the fan is considered positive since the pressure increases along the direction of the flow and the pressure difference across the ventilation opening is negative because there is a pressure decrease along the direction of flow.<br \/>\n<!--more continue&gt;&gt;--><br \/>\n<img src='http:\/\/s.wordpress.com\/latex.php?latex=%5Cdisplaystyle%5CDelta%20P_%7Bfan%2A%7D%2B%5CDelta%20P_%7Bhs%7D%3D0&bg=ffffff&fg=000000&s=0' alt='Latex formula' title='Latex formula' class='latex' \/>\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 (2)<\/p>\n<p><a href=\"http:\/\/www.heatsinkcalculator.com\/blog\/wp-content\/uploads\/2014\/09\/modified_fan_curve_calculation.png\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-253\" src=\"http:\/\/www.heatsinkcalculator.com\/blog\/wp-content\/uploads\/2014\/09\/modified_fan_curve_calculation.png\" alt=\"modified fan curve calculation\" width=\"593\" height=\"206\" srcset=\"https:\/\/www.heatsinkcalculator.com\/blog\/wp-content\/uploads\/2014\/09\/modified_fan_curve_calculation.png 593w, https:\/\/www.heatsinkcalculator.com\/blog\/wp-content\/uploads\/2014\/09\/modified_fan_curve_calculation-300x104.png 300w\" sizes=\"auto, (max-width: 593px) 100vw, 593px\" \/><\/a><br \/>\nFigure 1. Modified fan curve calculation in MSExcel<\/p>\n<p>Figure 1 shows an example of the calculation carried out using MSExcel. The values of \u0394P<sub>fan<\/sub>-\u0394P<sub>vent<\/sub> decrease until eventually the values turn negative. In order to create the modified fan curve the value of Q at which \u0394P<sub>fan<\/sub>-\u0394P<sub>vent<\/sub>=0 must be determined. This point lies between the two data points circled in red in Figure 1. To calculate this value of Q we will assume that the function is linear between each data point.\u00a0 The <em>INTERCEPT<\/em> function in MSExcel is used to estimate the value of Q when \u0394P<sub>fan<\/sub>-\u0394P<sub>vent<\/sub>=0. The <em>INTERCEPT<\/em> function takes two y points and two x points that lie on a straight line and calculates the point at which the line intersects the y-axis. The function\u00a0<em>INTERCEPT(A7:A8,D7:D8)<\/em> is entered in cell F8 to calculate the value of Q at \u0394P<sub>fan<\/sub>-\u0394P<sub>vent<\/sub>=0. The values of Q and \u0394P<sub>fan<sup>*<\/sup><\/sub> are entered as the modified fan curve data.<\/p>\n<p>Shown in figure 2 is a graph of the data shown in table 1. The addition of the pressure drops across the ventilation openings reduces the pressure difference across the fan at the same volumetric flow rate.<\/p>\n<p><a href=\"http:\/\/www.heatsinkcalculator.com\/blog\/wp-content\/uploads\/2014\/09\/modified_fan_curve1.png\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone size-full wp-image-254\" src=\"http:\/\/www.heatsinkcalculator.com\/blog\/wp-content\/uploads\/2014\/09\/modified_fan_curve1.png\" alt=\"modified fan curve\" width=\"566\" height=\"331\" srcset=\"https:\/\/www.heatsinkcalculator.com\/blog\/wp-content\/uploads\/2014\/09\/modified_fan_curve1.png 566w, https:\/\/www.heatsinkcalculator.com\/blog\/wp-content\/uploads\/2014\/09\/modified_fan_curve1-300x175.png 300w\" sizes=\"auto, (max-width: 566px) 100vw, 566px\" \/><\/a><\/p>\n<p>Figure 2. Graph of pressure difference versus volumetric flow rate for the original and modified fan curves<\/p>\n<p>&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>The HeatSinkCalculator includes an option to input a fan curve of the fan used to cool the heat sink. This [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"footnotes":""},"categories":[1],"tags":[],"class_list":["post-232","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/www.heatsinkcalculator.com\/blog\/wp-json\/wp\/v2\/posts\/232","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.heatsinkcalculator.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.heatsinkcalculator.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.heatsinkcalculator.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.heatsinkcalculator.com\/blog\/wp-json\/wp\/v2\/comments?post=232"}],"version-history":[{"count":23,"href":"https:\/\/www.heatsinkcalculator.com\/blog\/wp-json\/wp\/v2\/posts\/232\/revisions"}],"predecessor-version":[{"id":651,"href":"https:\/\/www.heatsinkcalculator.com\/blog\/wp-json\/wp\/v2\/posts\/232\/revisions\/651"}],"wp:attachment":[{"href":"https:\/\/www.heatsinkcalculator.com\/blog\/wp-json\/wp\/v2\/media?parent=232"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.heatsinkcalculator.com\/blog\/wp-json\/wp\/v2\/categories?post=232"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.heatsinkcalculator.com\/blog\/wp-json\/wp\/v2\/tags?post=232"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}