Plate frame and bar plate evaporator model validation and volume minimization
Date
2019
Authors
Simon, John Robert, III, author
Bandhauer, Todd M., advisor
Quinn, Jason, committee member
Carter, Ellison, committee member
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Abstract
Vapor compression chillers are the primary cooling technology for large building applications. Chillers have a large up front capital cost, with the heat exchangers accounting for the majority of the cost. Heat exchanger cost is a function of size, and therefore, a reduction in heat exchanger size can be correlated to a reduction in chiller capital cost. Few investigations focus on the reduction in heat exchanger size for vapor compression systems. Therefore, this investigation aims to decrease the size of chillers by predicting the minimum evaporator volume for a fixed performance. Only the evaporator was minimized because it was assumed that a similar process could be performed for the condenser in a future study. The study focused on a simple vapor compression cycle, and implemented high fidelity heat exchanger models for two compact heat exchanger types: brazed bar plate and gasketed plate and frame. These models accounted for variable fluid properties, phase change, and complex geometries within the evaporator core. The models used in this investigation were developed based on liquid-coupled evaporators in an experimental vapor compression system, and validated using collected data. The bar plate model was validated based on sizing and pressure drop to mean absolute errors of 14.2% and 14.0%, respectively. The plate frame model was validated for sizing to mean absolute errors equal to 7.9%; however, due to measurement uncertainty, pressure drop was not validated. The heat exchanger models were integrated into a simple vapor compression cycle model to determine the minimum required evaporator volume. Both heat exchanger types, in parallel and counter flow arrangements were minimized in this study. The minimum volume was achieved by varying the ratio between core length and number of channels. It was found that for both heat exchanger types, the parallel flow arrangement resulted in a smaller volume than the counter flow arrangement. Furthermore, the bar plate heat exchanger resulted in an optimum volume 91% smaller than the plate frame counterpart.
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Subject
plate frame heat exchanger
bar plate heat exchanger
vapor compression