Chilled water systems with large temperature differences are important for the design of energy-saving heating

ventilation

and air-conditioning systems

as they can reduce the energy consumption of chilled water pumps. However

the water-side heat transfer coefficient of the evaporator gradually decreases as the design temperature difference increases

and the chilled water flow rate decreases. This has become the main factor limiting the energy efficiency of chillers. In this study

the effect of the large temperature difference on the heat transfer performance of the evaporator is analyzed theoretically according to the heat transfer mechanism of the evaporator. The influence of different water circuit passes on the performance of centrifugal chillers designed with large temperature differences was compared experimentally in which the chillers were run in series. The results showed that

under the design conditions of a 10 ℃ temperature difference

the efficiency of the chillers in series can achieve a 6% improvement when the evaporators use dual passes rather than a single pass. The efficiency of the whole unit is optimized when the load proportion of the upstream and downstream units is approximately 55%:45%

owing to the intermediate temperature of the series scheme.