Abstract: The design water temperature (TSEC) of essential service water system is an important parameter affecting the thermal design of the cold chain heat exchanger. With the increasing of TSEC, the thermal design conditions of the cold chain heat exchanger tend to be bad, resulting in a gradual increasing in heat exchange area and equipment size. This paper takes the typical thermal design condition of the cold chain heat exchanger as the design input. For the different TSEC, the thermal hybrid design method is adopted to obtain the plate solutions of the cold chain heat exchanger. The number of total channels of the cold chain heat exchanger, the proportion of channels, and the total heat transfer coefficient with TSEC are analyzed. It was found that for specific thermal design conditions, the cold chain heat exchanger can only achieve a perfect match of pressure drop and heat transfer margin within a certain TSEC range, and there is a critical temperature. When TSEC is higher than this temperature, the number of plates will increase rapidly, and TSEC should be avoided as much as possible above this critical temperature.