{"id":4697,"date":"2026-09-20T18:14:06","date_gmt":"2026-09-21T01:14:06","guid":{"rendered":"https:\/\/www.26yc.com\/specific-heat-density-air\/"},"modified":"2026-10-09T17:56:59","modified_gmt":"2026-10-10T00:56:59","slug":"specific-heat-density-air","status":"publish","type":"post","link":"https:\/\/www.26yc.com\/zh_cn\/specific-heat-density-air\/","title":{"rendered":"Specific Heat &amp; Density of Air in Recovery Math"},"content":{"rendered":"<h2>The two numbers you reuse constantly<\/h2>\n<ul>\n<li><strong>Specific heat of air, cp<\/strong>: about 1.006 kJ\/kg.K (or 1006 J\/kg.K).<\/li>\n<li><strong>Density of air, rho<\/strong>: about 1.2 kg\/m3 at 20 degC and 1 atm.<\/li>\n<\/ul>\n<p>Together they give a volumetric heat capacity of roughly 1200 J\/m3.K &#8211; the energy stored in each cubic metre of air per degree of temperature.<\/p>\n<h2>The power equation<\/h2>\n<p>For any recovery duty the sensible power is:<\/p>\n<p><code>Q = rho x volumetric_flow x cp x temperature_difference<\/code><\/p>\n<p>Example: 1 m3\/s of air cooled by 10 K recovers about 1.2 x 1 x 1006 x 10 \u2248 12,100 W, or 12.1 kW. Multiply by operating hours and effectiveness to get daily energy, the input to any <a href=\"\/zh_cn\/heat-recovery-payback-calculation\/\">\u6295\u8d44\u56de\u6536\u671f\u8ba1\u7b97<\/a>.<\/p>\n<h2>Why constants still need care<\/h2>\n<p>Density falls as air heats and rises with pressure, so high-temperature or high-altitude duties shift the numbers. The <a href=\"\/zh_cn\/ntu-effectiveness-method\/\">epsilon-NTU method<\/a> folds these into the capacity rates, but the underlying cp and rho are where every estimate starts.<\/p>\n<h2>Frequently asked questions<\/h2>\n<p><strong>Do I use cp of dry or moist air?<\/strong> Use moist-air cp (~1.01) for ventilation work; the difference is small but real at high humidity.<\/p>\n<p><strong>Why is volumetric capacity useful?<\/strong> Because fans and ducts are sized by volume flow, not mass flow, so Q per m3\/s per K is the quick design figure.<\/p>\n<p>Need help specifying the right air-to-air heat recovery for your project? <a href=\"\/zh_cn\/contact-us\/\">Contact the QIYU engineering team<\/a> &#8211; WhatsApp +86 157 5335 5505, or email kuns913@gmail.com.<\/p>\n<p class=\"yc-faq-title\"><strong>\u5e38\u89c1\u95ee\u9898<\/strong><\/p>\n<div class=\"yc-faq\">\n<h3>What specific heat of air do recovery calculations use?<\/h3>\n<p>About 1.006 kJ per kg per K for dry air at room conditions; with moisture present you use the humid-air value, but 1.006 is the standard sensible-heat constant.<\/p>\n<\/div>\n<div class=\"yc-faq\">\n<h3>Why does air density matter in recovery?<\/h3>\n<p>Heat carried equals density times specific heat times flow times temperature difference; density converts volumetric flow to mass flow, and mass flow is what actually carries the energy across the core.<\/p>\n<\/div>\n<div class=\"yc-related\">\n<h3>\u76f8\u5173\u6587\u7ae0<\/h3>\n<ul>\n<li><a href=\"https:\/\/www.26yc.com\/zh_cn\/thermal-transmittance-u-value\/\" title=\"Thermal Transmittance (U-Value): The Building-Side Number Recovery Reduces\">Thermal Transmittance (U-Value): The Building-Side Number Recovery Reduces<\/a><\/li>\n<li><a href=\"https:\/\/www.26yc.com\/zh_cn\/ashrae-241-clean-air-rate\/\" title=\"ASHRAE 241: Controlling Infectious Aerosols with Equivalent Clean Airflow\">ASHRAE 241: Controlling Infectious Aerosols with Equivalent Clean Airflow<\/a><\/li>\n<\/ul>\n<\/div>","protected":false},"excerpt":{"rendered":"<p>The two numbers you reuse constantly Specific heat of air, cp: about 1.006 kJ\/kg.K (or 1006 J\/kg.K). Density of air, rho: about 1.2 kg\/m3 at 20 degC and 1 atm. Together they give a volumetric heat capacity of roughly 1200 J\/m3.K &#8211; the energy stored in each cubic metre of air per degree of temperature. [&hellip;]<\/p>\n","protected":false},"author":0,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[243,197],"tags":[295,282,199,296,294],"class_list":["post-4697","post","type-post","status-publish","format-standard","hentry","category-design-calc","category-encyclopedia","tag-air-density","tag-heat-transfer","tag-hvac","tag-mass-flow","tag-specific-heat"],"_links":{"self":[{"href":"https:\/\/www.26yc.com\/zh_cn\/wp-json\/wp\/v2\/posts\/4697","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.26yc.com\/zh_cn\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.26yc.com\/zh_cn\/wp-json\/wp\/v2\/types\/post"}],"replies":[{"embeddable":true,"href":"https:\/\/www.26yc.com\/zh_cn\/wp-json\/wp\/v2\/comments?post=4697"}],"version-history":[{"count":2,"href":"https:\/\/www.26yc.com\/zh_cn\/wp-json\/wp\/v2\/posts\/4697\/revisions"}],"predecessor-version":[{"id":5287,"href":"https:\/\/www.26yc.com\/zh_cn\/wp-json\/wp\/v2\/posts\/4697\/revisions\/5287"}],"wp:attachment":[{"href":"https:\/\/www.26yc.com\/zh_cn\/wp-json\/wp\/v2\/media?parent=4697"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.26yc.com\/zh_cn\/wp-json\/wp\/v2\/categories?post=4697"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.26yc.com\/zh_cn\/wp-json\/wp\/v2\/tags?post=4697"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}