# Heat exchanger and cooling towers design

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1. Nov 29, 2016

### Lazius

I was wondering all the assumptions I need to make regarding a design for a heat exchanger and cooling tower design from a IC engine testbed. Each engines average output is 55kW and the water jacket temperature is 80 degrees (C) and has to be cooled to 65 degrees (C). The ambient atmospheric condition of 24 degrees (C) d.b. temperature and 65% relative humidity. there are 8 engine beds but only 6 would be expected to be operational. I also need to assume various other data and so I am confused. I was asked to ascertain reasonable flow and return temperature for the cooling tower and so forth which I dont see how I can without experience in the field.

Initially one of the assumptions I find i will need is the engine thermal efficiency which I calculated based on ideal otto cycle and some data from University of Washington data. The thermal efficiency came upto 37.5 %... I was wondering what other assumptions I need to make to design the heat exchanger and cooling tower

2. Nov 30, 2016

### oz93666

FIrst thing must be to find the heat carried away in cooling water from the engines , remember some heat will go in the exhaust gasses , and the engine will lose some in convection to the air ... experiment is the best way ... water flow rate , temp difference ....The hotter you keep the engine by low cooling water flow , the more efficiently the engine runs...

You assume RH 65%, this is very dry air... what will happen on humid days ? the cooling tower won't cool much , engine will over heat.

Best to avoid constructing a cooling tower ... if you have a stream or even a pond or swimming pool use this as a heat sink for the approx. 500KW of waste heat..

You are correct ,you need "experience in the field" too many variables to do it by theory alone...experiments are needed.