Which density should be used to calculate the cooling capacity from the enthalpy difference?

Thread Content

This post was last edited by Admi1049 on 2017-4-24 at 16:40. Please help me figure out this issue; thanks. I haven’t been able to find a clear definition or source for it. The cooling capacity is calculated using the laboratory air enthalpy difference method (GB/T7725): Q = L*(I1–I2) = L*ρ*(I1–I2)/(1+X). Here, the state parameters refer to the air flow rate, specific volume of moist air (air density), and absolute humidity at the measurement point, and this is explained quite clearly. Under normal circumstances, given the wet and dry bulb temperatures of the inlet and outlet air, as well as the air volume, the cooling capacity Q can be calculated using the enthalpy difference method: Q = G(I1 – I2), where G is the mass flow rate of air, and G = air volume * density. So how should this density value be determined? Should the average density of air, 1.2, be used, or should the density of the air on the intake side or the exhaust side be taken? Should we use the average density for the inlet and outlet conditions? The air volume remains constant, but the air density on the inlet and outlet sides is different.