Numerical Study Of The Heat And Mass Transfer Exchanger In M-cycle :Analysis Using A Modified ?-NTU Method

In this paper, basis on the method in the sensible heat transfer process, analysis the efficiency of improved traditional single-stage indirect evaporative cooling. And put forward an efficiency calculation method, which is suitable for M-cycle of indirect evaporative cooling, and obtain the system exchange efficiency calculation formula of multi-channel series according to mathematical method of substitution.First of all, deduce sensible heat transfer process efficiency of counter-flow in detail, based on the theory of heat transfer in heat exchanger design and checking. And then introduce the improved the efficiency calculation method of single-stage regenerative indirect evaporative cooling. In this calculation formula, performance is concerned with the dry-bulb temperature at the inlet and outlet and the wet-bulb temperature of secondary air at inlet.According to the wet-bulb efficiency of indirect evaporative cooling in ASHRAE standard, performance is concerned with the dry-bulb temperature at the inlet and outlet and the wet-bulb temperature of secondary air at inlet. Based on the method, deduce wet-bulb efficiency of M-cycle indirect evaporative cooling, with the temperature mathematic substitution. And make reasonable assumptions for some of these variables, in order to get more simplified function expression for system. Compared with the traditional indirect evaporative cooling efficiency expression, this type replace the secondary air inlet wet bulb temperature variable with air import substitution wet bulb temperature, avoids the variable situation and iteration which is not easy to get, and combine M-cycle system efficiency with indirect evaporative wet-bulb cooling efficiency.Test using a heat exchanger, which inlet air mass flow rate of 0.00387 kg/s, secondary air mass flow rate of 0.00232 kg/s, the final product air mass flow rate is 0.00155 kg/s, and regard it as 1?2?3 channels system, respectively. Calculate the efficiency of M-cycle system and verify the function expression and the rationality of the assumption.In addition, according to control the variables(channel number, NTU and Cr), using of derived type and combining with the actual engineering application analyze M-cycle system performance of heat and mass transfer, fixing NTU and Cr for different systems and conclude to more channels systems. Provide theoretical basis for the heat exchanger size and energy consumption of equipment optimization.Finally, calculate the system in the thermal efficiency of indirect evaporative cooling system, and compared the two kinds of system efficiency calculation, analyze advantage of using in the form of the M-cycle system when heat exchanger layout section is multiple channels form. Based on the theory and the calculation results, make comprehensive evaluation to M-cycle system, analyze the feasibility and application prospect.