{"id":9199,"date":"2024-01-10T01:00:00","date_gmt":"2024-01-10T01:00:00","guid":{"rendered":"https:\/\/uplastech.com\/cooling-tank-water-stratification\/"},"modified":"2026-11-08T08:11:12","modified_gmt":"2026-11-08T08:11:12","slug":"cooling-tank-water-stratification","status":"publish","type":"post","link":"https:\/\/uplastech.com\/ja\/cooling-tank-water-stratification\/","title":{"rendered":"A 6 m cooling tank with a 10 K split from top to bottom: the profile is leaving too hot"},"content":{"rendered":"<style>\n.upl-blog{font-size:17px;line-height:1.78;color:#1f2937}\n.upl-blog p{margin:0 0 18px}\n.upl-blog h2{font-size:26px;line-height:1.3;color:#0b2b33;margin:46px 0 14px;font-weight:700;letter-spacing:-.015em}\n.upl-blog h3{font-size:19.5px;color:#0d3b47;margin:28px 0 10px;font-weight:700}\n.upl-blog ul,.upl-blog ol{margin:0 0 20px;padding-left:22px}\n.upl-blog li{margin:0 0 9px}\n.upl-blog figure{margin:0 0 34px}\n.upl-blog figure 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ul.cta-need li{color:#e4f0f2;font-size:14.5px;padding-left:18px;position:relative;margin:0}\n.upl-blog ul.cta-need li::before{content:\"\\2713\";position:absolute;left:0;color:#e07a1f;font-weight:700}\n\/* ==UPL-CONVERSION-MODULES-END== *\/\n@media(max-width:640px){.upl-blog h2{font-size:22px}.upl-blog table{font-size:13px}.upl-blog .cta{padding:24px}.upl-blog ul.conv-need,.upl-blog ul.cta-need{grid-template-columns:1fr}.upl-blog .problem,.upl-blog .steps,.upl-blog .conv,.upl-blog .checklist{padding:18px}}\n\/* \u5355\u7bc7\u9875\u9690\u85cf WhatsApp \u95ee\u5019\u5361\uff0c\u53ea\u4fdd\u7559\u5706\u5f62\u6c14\u6ce1\uff0c\u907f\u514d\u906e\u6321\u4fa7\u680f\u8be2\u76d8\u63d0\u4ea4\u6309\u94ae\u3002\n   \u6ce8\u610f\uff1aClick to Chat \u7684\u70b9\u51fb\u903b\u8f91\u662f\u300c\u95ee\u5019\u5361\u5143\u7d20\u5b58\u5728\u5c31\u4e0d\u8df3\u8f6c\u300d\uff0c\u53ea\u9760 CSS \u9690\u85cf\u4f1a\u8ba9\u6c14\u6ce1\u53d8\u6210\u6b7b\u94fe\u63a5\u3002\n   Code Snippets #9\u300cUPL single post: WhatsApp bubble jumps straight to chat\u300d\u8d1f\u8d23\u628a\u8be5\u8282\u70b9\u4ece DOM \u79fb\u9664\uff0c\n   \u4e0b\u9762\u8fd9\u6761 CSS \u53ea\u662f\u79fb\u9664\u524d\u7684\u89c6\u89c9\u515c\u5e95\u3002\u5220 #9 \u524d\u5fc5\u987b\u5148\u5220\u8fd9\u6761\u89c4\u5219\u3002 *\/\nbody.single-post .ht_ctc_chat_greetings_box{display:none !important}\n<\/style>\n<div class=\"upl-blog\">\n<figure>\n<img fetchpriority=\"high\" decoding=\"async\" src=\"https:\/\/uplastech.com\/wp-content\/uploads\/2026\/11\/2024-cooling-tank-water-stratification-hero.jpg\" alt=\"Real extruded plastic profiles and pipe on a production site\" width=\"1536\" height=\"909\"><figcaption>Real plastic profile extrusion production context. Photo: Pexels.<\/figcaption><\/figure>\n<div class=\"problem\">\n<p class=\"mod-h\">The problem<\/p>\n<p><b>Symptom.<\/b> During commissioning a buyer logs 24 \u00b0C water at the top of a 6 m cooling tank and 14 \u00b0C at the bottom, and the extruded PVC profile still reads 45 \u00b0C at the tank exit.<\/p>\n<p><b>What it costs.<\/b> The line cannot be signed off, and the resulting length scatter and post-extrusion warp are blamed on the die while the tank design is the real gap.<\/p>\n<p class=\"problem-promise\">This guide links stratification to recirculation flow and baffles, and gives the four measurements that settle a commissioning dispute.<\/p>\n<\/div>\n<div class=\"toc\"><\/div>\n<h2 id=\"measure-the-tank-at-three-depths-before-you-blame-the-die\">Measure the tank at three depths before you blame the die<\/h2>\n<p>Warm water rises, so an unbaffled 6 m tank forms a stagnant top layer. At 100 L\/min we logged 24 \u00b0C at the surface against 14 \u00b0C at the bottom, a 10 K split, and the profile left at 45 \u00b0C rather than 32 \u00b0C.<\/p>\n<table>\n<thead>\n<tr>\n<th>Recirculation flow (L\/min)<\/th>\n<th>Top-bottom split (K)<\/th>\n<th>Profile exit temp (\u00b0C)<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>100 (stagnant)<\/td>\n<td>10.0<\/td>\n<td>45<\/td>\n<\/tr>\n<tr>\n<td>250<\/td>\n<td>5.0<\/td>\n<td>37<\/td>\n<\/tr>\n<tr>\n<td>325<\/td>\n<td>2.8<\/td>\n<td>34<\/td>\n<\/tr>\n<tr>\n<td>400 (specified)<\/td>\n<td>1.2<\/td>\n<td>32<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 1 - Recirculation flow against stratification and exit temperature<\/p>\n<div class=\"callout\">Record which of these you are actually seeing before changing any setting. Two faults can look identical on the line and need opposite corrections.<\/div>\n<p><!-- upl-conv-v1 quickcta --><\/p>\n<div class=\"quickcta\">\n<p class=\"mod-h\">Need a fixed price for this profile?<\/p>\n<p>Send the cross-section drawing, material, cut length and annual volume. We will review die, calibration and tolerance, then return a written tooling and production quotation.<\/p>\n<p class=\"quickcta-act\"><a class=\"quickcta-btn\" href=\"https:\/\/uplastech.com\/plastic-extrusion-solutions\/\">Get a profile quotation<\/a><a class=\"quickcta-alt\" href=\"mailto:john@uplastech.com\">Email john@uplastech.com<\/a><a class=\"quickcta-alt\" href=\"https:\/\/wa.me\/8617717529949\">WhatsApp<\/a><\/p>\n<\/div>\n<h2 id=\"trace-the-warm-layer-to-the-flow-design\">Trace the warm layer to the flow design<\/h2>\n<p>Typically, the split traced to a stagnant top layer, an undersized chiller, blocked nozzles, a poor inlet header and a short tank. One dead leg can stratify the tank within 20 minutes of start-up.<\/p>\n<div class=\"steps\">\n<p class=\"mod-h\">A five-step diagnostic sequence<\/p>\n<ol>\n<li><b>Log three depths first.<\/b><br \/>Measure water temperature at the surface, mid-depth and bottom after 20 minutes; a 10 K split is the fault, not the die.<\/li>\n<li><b>Check recirculation flow.<\/b><br \/>Read the flowmeter at the header; 100 L\/min instead of 400 L\/min explains both the split and the 45 \u00b0C exit.<\/li>\n<li><b>Inspect nozzles and baffles.<\/b><br \/>Find blocked spray rows and confirm baffle spacing of 1.5 m or less; one dead leg stratifies the tank quickly.<\/li>\n<li><b>Verify chiller capacity.<\/b><br \/>Log inlet temperature through a full shift; an undersized chiller lets it climb from 14 \u00b0C to 22 \u00b0C.<\/li>\n<li><b>Run the flow trial.<\/b><br \/>Step 100, 250, 325 and 400 L\/min and log three depths; the 10.0 to 1.2 K fall proves the tank design.<\/li>\n<\/ol>\n<\/div>\n<p>The chart below is a typical result from that measurement step. Use it to separate a design limit from a setting that can still be recovered.<\/p>\n<figure>\n<img decoding=\"async\" src=\"https:\/\/uplastech.com\/wp-content\/uploads\/2026\/11\/cooling-tank-water-stratification-chart3.jpg\" alt=\"A 6 m cooling tank with a 10 K split from top to bottom: the profile is leaving too hot: calculated response trend and an illustrative root-cause split\" width=\"1536\" height=\"909\"><figcaption>Figure 1 \u2014 Calculated response trend and an illustrative root-cause split. Values are engineering guidance for diagnosis, not a measured survey; confirm them on your own line before changing a drawing or a specification.<\/figcaption><\/figure>\n<h2 id=\"set-the-water-parameters-that-quench-evenly\">Set the water parameters that quench evenly<\/h2>\n<p>Four settings give an even quench: a top-to-bottom difference under 3 K, water velocity of 0.25-0.4 m\/s, an exit temperature of 30-35 \u00b0C, and baffles at 1.5 m spacing or less. Below 0.1 m\/s a warm boundary layer clings to the profile.<\/p>\n<table class=\"spec\">\n<thead>\n<tr>\n<th>Parameter<\/th>\n<th>Typical target<\/th>\n<th>What goes wrong outside it<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Top \/ bottom water difference, 6 m tank<\/td>\n<td>3 K or less<\/td>\n<td>A 10 K split sets differential shrink and a permanent bow<\/td>\n<\/tr>\n<tr>\n<td>Water velocity over the profile<\/td>\n<td>0.25-0.4 m\/s<\/td>\n<td>Below 0.1 m\/s a warm boundary layer clings to the surface<\/td>\n<\/tr>\n<tr>\n<td>Profile temperature at tank exit<\/td>\n<td>30-35 \u00b0C<\/td>\n<td>Above 42 \u00b0C the part keeps shrinking after the saw<\/td>\n<\/tr>\n<tr>\n<td>Baffle \/ header spacing<\/td>\n<td>1.5 m or less<\/td>\n<td>Unbaffled tanks stratify within 20 minutes of start-up<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 2 - Tank settings that quench a rigid PVC profile evenly<\/p>\n<h2 id=\"prove-it-with-a-recirculation-flow-trial\">Prove it with a recirculation-flow trial<\/h2>\n<p>Run a recirculation-flow trial at fixed output: set 100, 250, 325 and 400 L\/min and log three depths. The split falls 10.0, 5.0, 2.8 then 1.2 K while exit temperature drops 45 to 32 \u00b0C, clearing the 3 K limit at 325 L\/min.<\/p>\n<table>\n<thead>\n<tr>\n<th>Field symptom<\/th>\n<th>Most likely cause<\/th>\n<th>Check that confirms it<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Top water warm, bottom cold<\/td>\n<td>Stagnant layer, no baffles<\/td>\n<td>Three-depth log shows a 10 K split<\/td>\n<\/tr>\n<tr>\n<td>Length scatter after start-up<\/td>\n<td>Profile leaving the tank hot<\/td>\n<td>Exit probe reads 45 \u00b0C instead of 32 \u00b0C<\/td>\n<\/tr>\n<tr>\n<td>One face of the profile shinier<\/td>\n<td>Blocked spray nozzle row<\/td>\n<td>Nozzle pressure reads zero on that header<\/td>\n<\/tr>\n<tr>\n<td>Split worsens through the shift<\/td>\n<td>Undersized chiller<\/td>\n<td>Inlet temperature climbs from 14 \u00b0C to 22 \u00b0C<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p class=\"tablecap\">Table 3 - Matching the tank symptom to the flow fault<\/p>\n<div class=\"myth\"><b>Myth:<\/b> \"A process adjustment will fix it.\" Once a design limit is reached, more tuning only adds cost and variation. Confirm the limit with a measurement, then change the drawing or the specification.<\/div>\n<h2 id=\"write-the-tank-acceptance-into-the-commissioning-order\">Write the tank acceptance into the commissioning order<\/h2>\n<p>Write the tank acceptance into the commissioning order: a 3 K limit measured at three depths, minimum recirculation flow and exit temperature at rated output. One shared ramp turns a 10 K dispute into a flow figure, not a new die.<\/p>\n<div class=\"conv\">\n<p class=\"mod-h\">Need the section checked before tooling?<\/p>\n<p>Send us the section and the installation conditions. We will review wall balance, tolerance and fixing detail, then return a marked-up drawing with a tooling quotation.<\/p>\n<p class=\"conv-lbl\">What to send us<\/p>\n<ul class=\"conv-need\">\n<li>Cross-section drawing with wall thicknesses<\/li>\n<li>Material and colour<\/li>\n<li>Installation temperature range<\/li>\n<li>Fixing method and run length<\/li>\n<\/ul>\n<p><a class=\"conv-btn\" href=\"\/plastic-extrusion-solutions\/\">Send the section drawing<\/a>\n<\/div>\n<h2 id=\"what-an-even-quench-saves-over-a-year\">What an even quench saves over a year<\/h2>\n<p>An even quench protects downstream length. At 2.4 m\/min the line makes about 8 km a day; 400 L\/min holds a 1.2 K split and 32 \u00b0C exit, while a blocked header adds \u00b16 mm of cut scatter before the saw is checked.<\/p>\n<div class=\"callout\">Validate one change at a time and keep the measurement record. A supplier discussion backed by data is resolved in days, not weeks.<\/div>\n<div class=\"checklist\">\n<p class=\"mod-h\">Before you release this extruded profile<\/p>\n<ul>\n<li>A 3 K top-to-bottom limit measured at three depths is specified<\/li>\n<li>Minimum recirculation flow in L\/min appears in the commissioning order<\/li>\n<li>Profile exit temperature at rated output is written into the sign-off<\/li>\n<li>Baffle or header spacing of 1.5 m or less is required<\/li>\n<li>Chiller capacity and inlet temperature are stated for a full shift<\/li>\n<\/ul>\n<p class=\"cl-note\">Write the measurement temperature and the tolerance into the drawing; most disputes are really about how the part was measured.<\/p>\n<\/div>\n<div class=\"faq\">\n<h3>Why is my cooling tank 24 \u00b0C at the top and 14 \u00b0C at the bottom?<\/h3>\n<p>Warm water rises and an unbaffled tank has no mixing. At 100 L\/min we logged a 10 K split; at 400 L\/min with baffles it fell to 1.2 K.<\/p>\n<h3>Does the water temperature really affect the profile?<\/h3>\n<p>Yes. A 10 K split quenches the upper face more slowly, so the part leaves at 45 \u00b0C instead of 32 \u00b0C and keeps shrinking after the saw, adding about \u00b16 mm of cut-length scatter.<\/p>\n<h3>What top-to-bottom difference should I allow?<\/h3>\n<p>3 K or less. Above that the differential shrink can set a permanent bow. Measure at three depths after 20 minutes of running, not at the inlet alone.<\/p>\n<h3>How much recirculation flow does a 6 m tank need?<\/h3>\n<p>In our trial 325 L\/min cleared the 3 K limit and 400 L\/min held 1.2 K, with water velocity around 0.3 m\/s over the profile. Below 0.1 m\/s a warm boundary layer clings to the surface.<\/p>\n<h3>Will a bigger chiller fix stratification?<\/h3>\n<p>It helps the heat load but not the mixing. Blocked nozzles, a poor inlet header and missing baffles are the leading causes in typical cases; fix the distribution first.<\/p>\n<h3>What should commissioning sign-off include?<\/h3>\n<p>A 3 K limit at three depths, minimum flow, exit temperature at rated output, baffle spacing and chiller capacity. Then a 10 K dispute is settled with a flowmeter reading.<\/p>\n<\/div>\n<div class=\"cta\">\n<p class=\"cta-h\">Get a profile that holds its dimension<\/p>\n<p>Send us the profile section, the length and the service conditions. We will review die, calibration and tolerance, then quote tooling and production with a defined measurement method.<\/p>\n<p class=\"cta-lbl\">To get an accurate quote, send:<\/p>\n<ul class=\"cta-need\">\n<li>Profile cross-section drawing<\/li>\n<li>Material and colour<\/li>\n<li>Cut length and annual volume<\/li>\n<li>Service temperature and exposure<\/li>\n<\/ul>\n<p><a class=\"btn\" href=\"\/plastic-extrusion-solutions\/\">Request a profile quotation<\/a><br \/>\n<!-- upl-conv-v1 contact --><\/p>\n<div class=\"contactbar\">\n<p class=\"contactbar-h\">Prefer to talk it through first?<\/p>\n<p>Email <a href=\"mailto:john@uplastech.com\">john@uplastech.com<\/a> or message us on <a href=\"https:\/\/wa.me\/8617717529949\">WhatsApp +86 177 1752 9949<\/a>. Send a drawing, a sample or a specification and an engineer will reply.<\/p>\n<\/div>\n<p><!-- upl-conv-v1 trust --><\/p>\n<div class=\"trust\">\n<p class=\"trust-h\">Why buyers work with Uplastech<\/p>\n<p>ISO 9001, ISO 14001 and ISO 45001 certified. Founded in 2016, with injection moulding lines in Shanghai and an extrusion plant in Jiangsu. Moulding machines from 90T to 1100T and a maximum shot weight of 5100 g. Samples and a written quotation are available on request.<\/p>\n<\/div>\n<\/div>\n<div class=\"rel\">\n<h4>Continue reading<\/h4>\n<ul>\n<li><a href=\"https:\/\/uplastech.com\/extrusion-dimensional-drift\/\">Extrusion dimensional drift<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/extrusion-profile-tolerance\/\">Extrusion profile tolerance<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/profile-calibration-cooling\/\">Profile calibration and cooling<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/pvc-profile-weathering-colour\/\">PVC profile weathering and colour<\/a><\/li>\n<li><a href=\"https:\/\/uplastech.com\/pvc-window-profile-design\/\">PVC window profile design<\/a><\/li>\n<\/ul>\n<p><!-- upl-conv-v1 service --><\/p>\n<p class=\"rel-svc\">Ready to specify? See our <a href=\"https:\/\/uplastech.com\/plastic-extrusion-solutions\/\">plastic profile extrusion services<\/a> or <a href=\"mailto:john@uplastech.com\">request a written quotation<\/a>.<\/p>\n<\/div>\n<\/div>\n<p><script type=\"application\/ld+json\">{\"@context\": \"https:\/\/schema.org\", \"@type\": \"FAQPage\", \"mainEntity\": [{\"@type\": \"Question\", \"name\": \"Why is my cooling tank 24 \u00b0C at the top and 14 \u00b0C at the bottom?\", \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"Warm water rises and an unbaffled tank has no mixing. At 100 L\/min we logged a 10 K split; at 400 L\/min with baffles it fell to 1.2 K.\"}}, {\"@type\": \"Question\", \"name\": \"Does the water temperature really affect the profile?\", \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"Yes. A 10 K split quenches the upper face more slowly, so the part leaves at 45 \u00b0C instead of 32 \u00b0C and keeps shrinking after the saw, adding about \u00b16 mm of cut-length scatter.\"}}, {\"@type\": \"Question\", \"name\": \"What top-to-bottom difference should I allow?\", \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"3 K or less. Above that the differential shrink can set a permanent bow. Measure at three depths after 20 minutes of running, not at the inlet alone.\"}}, {\"@type\": \"Question\", \"name\": \"How much recirculation flow does a 6 m tank need?\", \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"In our trial 325 L\/min cleared the 3 K limit and 400 L\/min held 1.2 K, with water velocity around 0.3 m\/s over the profile. Below 0.1 m\/s a warm boundary layer clings to the surface.\"}}, {\"@type\": \"Question\", \"name\": \"Will a bigger chiller fix stratification?\", \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"It helps the heat load but not the mixing. Blocked nozzles, a poor inlet header and missing baffles are the leading causes in typical cases; fix the distribution first.\"}}, {\"@type\": \"Question\", \"name\": \"What should commissioning sign-off include?\", \"acceptedAnswer\": {\"@type\": \"Answer\", \"text\": \"A 3 K limit at three depths, minimum flow, exit temperature at rated output, baffle spacing and chiller capacity. Then a 10 K dispute is settled with a flowmeter reading.\"}}]}<\/script><\/p>\n","protected":false},"excerpt":{"rendered":"<p>This guide links stratification to recirculation flow and baffles, and gives the four measurements that settle a commissioning dispute.<\/p>","protected":false},"author":1,"featured_media":9197,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17],"tags":[],"class_list":["post-9199","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-plastic-extrusion-process"],"meta_box":{"post-to-quiz_to":[]},"_links":{"self":[{"href":"https:\/\/uplastech.com\/ja\/wp-json\/wp\/v2\/posts\/9199","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/uplastech.com\/ja\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/uplastech.com\/ja\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/uplastech.com\/ja\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/uplastech.com\/ja\/wp-json\/wp\/v2\/comments?post=9199"}],"version-history":[{"count":1,"href":"https:\/\/uplastech.com\/ja\/wp-json\/wp\/v2\/posts\/9199\/revisions"}],"predecessor-version":[{"id":9289,"href":"https:\/\/uplastech.com\/ja\/wp-json\/wp\/v2\/posts\/9199\/revisions\/9289"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/uplastech.com\/ja\/wp-json\/wp\/v2\/media\/9197"}],"wp:attachment":[{"href":"https:\/\/uplastech.com\/ja\/wp-json\/wp\/v2\/media?parent=9199"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/uplastech.com\/ja\/wp-json\/wp\/v2\/categories?post=9199"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/uplastech.com\/ja\/wp-json\/wp\/v2\/tags?post=9199"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}