蒸发式空冷器强化传热性能

摘要

The evaporative air cooler is a complex system whose essential components comprise heat exchanger pipe coil,circulation water pump and fan.As these essential components interact within the system,the optimal combination of which is significant for heat transfer enhancement.The effects of circulation water pump frequency, fan frequency,inlet temperature and fluid rate of the process fluid on the heat transfer performance of evaporative air coolers were experimentally studied.The results show that the heat transfer rate and united heat transfer coefficient outside the tubes all increase continuously with the inlet temperature of the process fluid rising.When the hot water pump frequency increases,the united heat transfer coefficient outside the tubes is unchanged,but the heat transfer rate accordingly increases to a certain extent,then remains stable.The effects of circulation water pump and fan frequencies on the heat transfer performance are not a simple positive correlation,and there exists an optimal coupling.When the inlet temperature of the process fluid is 50 ℃,the optimum heat transfer performance can be obtained as the circulation water pump frequency,the fan frequency and the hot water pump frequency are 30,45,42 Hz respectively.The concept of united heat transfer coefficient outside the tubes was presented and researched,which simplified the process calculation.The results provide the basis for the optimal design and operation of evaporative air coolers.%蒸发式空冷器是由换热盘管、循环水泵和风机等组成的一个复杂系统，系统内部各部件相互影响，优化组合对强化传热至关重要。实验研究了循环水泵频率、风机频率、管内流体进口温度和热水泵频率等因素对蒸发式空冷器传热性能的影响。结果表明：管内流体进口温度增加时，传热速率和管外联合传热系数均呈现持续增加的趋势；热水泵频率增加时，管外联合传热系数基本没有变化，但传热速率随之增加，增加到一定程度后趋于稳定不变；循环水泵和风机频率的变化对传热性能的影响并非简单的正相关关系，二者存在一个最佳的耦合；当管内流体进口温度为50℃时，实验确定在循环水泵频率为30 Hz，风机频率为45 Hz，热水泵频率为42 Hz时，系统的传热性能达到最优。对管外联合传热系数的研究，简化了工艺计算过程。研究结果为蒸发式空冷器的优化设计，以及节能优化操作提供了一定的依据。