Radiator question, for thermodynamics/heat transfer experts |
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Radiator question, for thermodynamics/heat transfer experts |
bondo |
Feb 2 2005, 12:26 AM
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Practicing my perpendicular parking Group: Members Posts: 4,277 Joined: 19-April 03 From: Los Osos, CA Member No.: 587 Region Association: Central California |
Hopefully I can get some input on this without too much of the inevitable "that won't work" (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)
I'm cutting down a large tall radiator into a shorter one.. 1/3 the height to be exact. The 3 layers of radiator will be set up in a cross flow, sequentially. The hottest water will enter the rearmost later, travel across, then across again in the middle layer, and across yet again in the front layer. The idea is the hottest water gets the hottest air, and the coldest water gets the coldest air. This way delta T stays pretty constant.. I'm thinking of it as trying to heat the air as much as possible, which would cool the water as much as possible. So I realize that cooling capacity will be reduced, as I will be dealing with 1/3 as much air. But then the cooling capacity must be more than 1/3, because it's 3 layers thick instead of 1. My question is what percentage of the original cooling capacity should I be expecting? Would it do me any good to do 5 layers instead of 3? (by adding 2/3 of a second radiator) The original radiator cooled the same engine just fine, in a heavier car, with an AC condenser preheating the air. I will be running an electric pump, so I will have an advantage at idle. |
ArtechnikA |
Feb 2 2005, 11:56 AM
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rich herzog Group: Members Posts: 7,390 Joined: 4-April 03 From: Salted Roads, PA Member No.: 513 Region Association: None |
"could," i think ... and yes, multipass heat exchangers change directions in vertical (typically? exclusively?) zones. (almost?) exclusively hot water enters at the bottom and cooled water is extracted from the top. this allows the flow to work with convection and promotes the coalescing of air bubbles at the top rather than remaining trapped in the moving fluid. testing is good... i'm with Mike, i think you'll find the cooling will be no better, and possibly worse, with 3 layers rather than two. i think you'll gain more from increased airflow with 2 layers than you may lose from another incremental pass due to the preheat effect. air is lazy, and at speed, will be happy to bypass the radiator core and go right over the car if internal restsrictions are too high. you can't blow air into a closed box. it's also more efficient to push air than pull it, and one problem with using extraction fans is that without really good sealed ducting, the air would much rather go around the core than through it. tends to preheat the fans too, although there are enough of them in service that the environment doesn't seem to adversely affect their life. (and it does have the plus that it does not shadow the core from incoming freestgream air...) |
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