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Bad idea to use a too big heat exchanger?

by TSN79
Tags: exchanger, heat
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TSN79
#1
Mar28-13, 04:56 PM
P: 357
I'm constructing a water based central heating system, and in it is a plate heat exchanger. People often tell me not to be scrimpy regarding its effect when picking one. But then I've heard others say that having a 150 kW heat exchanger - when the effect needed will never rise above 40 kW - is perhaps an even worse idea. Could someone give me some point about why it's a bad idea so I can relay?
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russ_watters
#2
Mar28-13, 05:29 PM
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It depends on the application. Often it is a significant benefit (lower pressure drop, more efficient heat exchange). When you say a "water based central heating system", what exactly do you mean? What is the heat source that heats the water via the plate heat exchanger?

An example where too big is a bad idea is a heating coil in a 100% outside air handling unit. Too big means low fluid velocity, means uneven surface temperature, means you can freeze the water in the coil even when it comes in very hot.
TSN79
#3
Mar28-13, 06:20 PM
P: 357
Quote Quote by russ_watters View Post
When you say a "water based central heating system", what exactly do you mean?
The hottest side of the exchanger comes from a district heating system (120C supply). The other side consist of a normal radiator system (supply/return 70-50C).

russ_watters
#4
Mar30-13, 03:25 PM
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P: 22,234
Bad idea to use a too big heat exchanger?

Oh, just water to water: Bigger is better. Just make sure you appropriately size any pumps or control valves .


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