# Total Surface Heat Flux in a Volume

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 February 8, 2017, 03:56 Total Surface Heat Flux in a Volume #1 New Member   Mickael Perrin Join Date: Feb 2017 Posts: 1 Rep Power: 0 Hello everyone, I am a student and I actually work with ansys Fluent on an heat exchanger : Water Charge Air Cooler in cross flow. The fluids are water (52.5°C) and air (220°C). The goal is to transfer heat from air to the water so after simulation, I need to export the heat flux. To avoid to research every contact surface, I use a volume integral to get the heat flux for every volume (air, water and aluminium) and then I multiply the heat flux (in W/m²) by the surface (m²) of each zone to get the real flux (W). However when I proceeds, the energy balance isnt zero : the flux lost by air isnt the same gained by the water. This is the geomtry i study : To limit the number of cells, i do a planar symmetry according to the plan ZX in the middle of the air pass. For exemple : - thickness aluminium : 1 mm everywhere. - lenght air : 30 mm - height air : 6 mm - width air : 2 mm - lenght water = width air + 2*thickness alu = 4 mm - height water = 1.6 mm - width water = lenght air - 2*thickness alu = 28 mm For this case, the air lose 0.87 W and the water get 0.86 W, (the aluminium at 0.0035 W is irrelevant acording to me) so there is a balance of 0.01W. Can someone tell me where it come from ? For this exemple the balance is about 0.01W but for some others, it can grow up to 0.3 W (the air lose 0.65 W but the water get 1,1W). Thanks everyone for your help and your time Cordially Mickael

 Tags heat exchanger, total surface heat flux, wcac