<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto">From looking at your parameters, I’m guessing that this doesn’t represent a real heat exchanger that you’re trying to match as you specify a horizontal tube bank and then only have one tube - and it’s 30 meters long. So unless your tank is 30 meters long this probably isn’t right. <div><br></div><div>So you’d like more heat transfer - so that means either more HX surface area or lower heat transfer resistance (or a bigger temperature difference but it sounds like you’re comfortable with those conditions). The pipes are copper and the Nusselt number parameters are pretty good (could go higher on the multiplier (maybe up to 1) and slightly higher on the exponent (maybe up to 0.3)) so your best bet is to add more tubes, make the tubes bigger, etc. </div><div><br></div><div>Like many questions asked here, the answer is usually along the line of “What would you do in real life to fix it”. Always start there as almost all TRNSYS models are based on the physics of the real equipment.</div><div><br></div><div>Jeff <br><br><div dir="ltr">Sent from my iPhone</div><div dir="ltr"><br><blockquote type="cite">On Jun 4, 2022, at 8:41 AM, Song Aoye via TRNSYS-users <trnsys-users@lists.onebuilding.org> wrote:<br><br></blockquote></div><blockquote type="cite"><div dir="ltr"><p style="font-family:Arial;">
Dear All,
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<span style="font-family:Arial;">Does anyone know how to set up the immersed heat exchanger so that its heat transfer capacity can be increased?</span>
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<span style="font-family:Arial;">My current setting is:</span>
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<span style="font-family:Arial;">Exchanger type horizontal tube bank</span><br>
<span style="font-family:Arial;">Fluid 20% Ethylene Glycol solution</span><br>
<span style="font-family:Arial;">Multiplier for Natural Convection Correlation 0.6</span><br>
<span style="font-family:Arial;">Exponent for Rayleigh Number 0.25</span><br>
<span style="font-family:Arial;">Geometry Factor 1</span><br>
<span style="font-family:Arial;">Geometry Factor Exponent 0</span><br>
<span style="font-family:Arial;">Tube lnner Diameter 0.098 m</span><br>
<span style="font-family:Arial;">Tube Outer Diameter 0.105 m</span><br>
<span style="font-family:Arial;">wall Conductivity 1440 kJ/h m K</span><br>
<span style="font-family:Arial;">Tube Length 30 m</span><br>
<span style="font-family:Arial;">Number of Tubes 1</span><br>
<span style="font-family:Arial;">Header volume 0.0226 m3</span><br>
<span style="font-family:Arial;">Cross Sectional Area 0.0075 m2</span><br>
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<span style="font-family:Arial;">This setting will make it difficult for the cold energy of the fluid in the exchanger to be transferred to the water tank. </span>
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<span style="font-family:Arial;">When the temperature difference between the <span style="font-family:Arial;white-space:normal;">fluid</span> in the <span style="font-family:Arial;white-space:normal;">exchanger</span> and the water outside is 5 <span style="font-family:Arial;white-space:normal;">°C</span>, the temperature of the fluid flowing into the <span style="font-family:Arial;white-space:normal;">exchanger</span> will only increase by 0.13 °C after it flows out. </span>
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<span style="font-family:Arial;">So how should I change the above parameters to make the heat transfer ability of this exchanger stronger?</span><br>
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