From the perspective of energy utilization, we always hope that the higher the exhaust temperature of the Refrigerated dryer is, the better it is. It is better to be the same as the inlet temperature. At this time, the "waste cooling" is zero. 

However, in fact, it is impossible to achieve this. It is not uncommon for the temperature difference between the inlet and outlet of the cold dryer to be more than 15 ℃. This is because: 

① energy is inevitably lost in the process of transmission and exchange; 

② The heat transfer coefficient of homogeneous gas with low temperature and small temperature difference is small in the convective heat transfer of the wall (especially in the downstream heat transfer); 

③ In the process of heat exchange, the cooling of saturated hot gas flow will inevitably be accompanied by phase change. A part of the total cooling capacity absorbed by it must be used to pay for the latent heat of phase change, thus limiting the temperature drop of hot gas flow. This in turn limits the rise of cold air flow temperature (especially in the case of downstream heat transfer)

Source: Eddie Electromechanical