Experimental and analytical investigation of transient behavior of coupled heat exchangers

In this paper, transient behavior of coupled heat exchangers subjected to sudden change in inlet temperature was studied experimentally and analytically. Coupled heat exchangers in which thermal energy is indirectly transferred between hot and cold fluids are widely used in industries. The investigated system is used in a power plant to shift heat from gas turbine components to the ambient air, using water as a circulating fluid. It consists of one-dimensional and two-dimensional flow heat exchangers. Effect of rapid reduction at inlet air temperature on the transient behavior of different fluid temperatures was investigated experimentally in real condition. Data acquired from experimental setup during transient condition was then compared with the results obtained from analytical simulation of the system. Comparison proved the analytical model has high accuracy and can predict transition time in various conditions. Furthermore, using the developed model the effect of some other parameters such as length of connection pipes, heat transfer coefficient of flow streams, mass flowrate of circulating flow-stream, on the transition time of the heat shifting system were investigated.