The aim of this project is to select appropriate heat exchangers out of available gas-gas heat exchangers for used in a proposed power plant. The heat exchangers are to be used in the power plant for the purposes of waste heat recovery, recuperation and intercooling.In selecting an optimum heat exchanger for use, the PCHE was identified as the best candidate for waste heat recovery and recuperation.
In order to ascertain the viability of this assertion the PCHE was designed and a 1D modeling performed in MATLAB using the conditions that the heat exchanger for waste heat recovery would be subjected to. The choice of using the conditions that the waste recovery heat exchanger would be subjected to was due to the fact that, it is the heat exchanger that would be subjected to much harsh conditions (thus higher temperatures of up to 650 ºC). The PFHE was also designed and similarly a 1D modeling performed in MATLAB.
The decision to consider the design of the PFHE was to offer a platform to compare and contrast the performance of the PCHE in order to have a strong basis for deciding on whether to stick to the choice for the PCHE or otherwise.The results obtained from the 1D modeling of the design of the heat exchangers indicates that the PCHE performed better with regards to pressure drops across the heat exchangers (with values of 1.17 and 2.47 % for the cold and hot sides respectively), compactness (with a value of 1300 m2/m3 for the PCHE compared to the 855 m2/m3 recorded from the PFHE), however the PFHE recorded higher heat transfer coefficients, and a subsequent higher overall transfer coefficient.
Results obtained from the simulation of the 3D model buttress the decision to employ the PCHE as heat exchangers to be used for waste heat recovery and recuperation as a wise one, with an effectiveness of 0.94 as against the design value of 0.90, and with pressure drops as desired of the optimum heat exchanger.
Author: Yakah, Noah