Need advice with Heat Exchanger

PoolGate said:

How big is the pool? 40kW is around 136k BTUs. While ok, that isn't a lot of heat to add to a large pool. My gas heater is 400k BTUs. Heat pumps have about the same performance and you are right at what heat pumps put out.

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Its 135k BTU indeed. The Pool is 27.000 Liters (or 7k Gallon). So, does the temperature output seems legit? I was expecting + 3 to 5C Degrees. And seems that if the hot water inlet is at 60-75 range the performace is almost the same.

I have an infrared meter, I will try and see if it is capable to measure it. But how does that plays a role?

PoolGate said:

It'll tell you roughly the efficiency of the heater. You'll have to look up what specific temp you are looking for.

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OK, I will try to! Thank you so much for your time here, really appreciated. However, regarding my initial question, is +1.5C temp difference acceptable;

mknauss said:

Outlet temperature is based on BTU output of the heater, flow rate through the heater, and efficiency of the exchanger.

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Hello again! Here are some specs for heat exchanger (40wW, 34.393kcal, 135.000btu) and the pump (kripsol KSE100, Q=15.4 m3/h, Qmax-21.6m3/h).
Is it possible to tell me if what I am getting is OK? All the piping is φ50.

Edit 1: the hot water is at 2.0bar, it circulates through a wilo pico 30/ 1-8 boiler pump. It has a Qmax at 4.4m3/hour and i am working it at middle scale, so I guess flow rate is about 2m3/h for the hot water at 65-75 degrees Celsius.

Edit 2: I provided chat GPT with the following data:
Cold fluid flow rate: 15 cubic meters per hour
Hot fluid flow rate: 2 cubic meters per hour
Cold fluid input: 25C
Hot fluid temperature: 65
Hot fluid output: 45
assume the fluid is water and calculater the COLD fluid output temperature.

The GPT responds that using the heat exchanger equations: Tout COLD is approximately 26.331°C. (attached)
Almost the same answer was given for Hot fluid temperature of 75C

I asked GPT: why there is no difference for Tout between 65 and 75 hot water input temperature?
GPT Reply:
The reason there's very little difference in the cold fluid output temperature between hot water input temperatures of 65°C and 75°C is primarily due to the relatively low flow rates of the hot fluid and cold fluid in this particular heat exchanger system.

In this scenario:

• Cold fluid flow rate is 15 cubic meters per hour.
• Hot fluid flow rate is only 2 cubic meters per hour.

When the flow rates are significantly different, the temperature change in the hot fluid has a limited effect on the cold fluid. The hot fluid has a higher temperature at the inlet, but because of its lower flow rate, it doesn't transfer as much heat to the cold fluid as it might with a higher flow rate. As a result, the difference in �out, coldTout, cold between 65°C and 75°C hot fluid input is relatively small.

To achieve a more significant change in Tput cold with varying hot fluid input temperatures, you might need to adjust the flow rates or use a more efficient heat exchanger. Higher flow rates on the hot side would increase heat transfer to the cold fluid and lead to a more noticeable difference in Tout cold with changes in hot fluid input temperature.