Performance of a run-around system for HVAC heat and moisture transfer applications using cross-flow plate exchangers coupled with aqueous lithium bromide

A two-dimensional steady-state mathematical model is developed to study the heat and water vapor transport in a run-around heat and moisture exchanger coupled with a lithium bromide solution for air-to-air exchanger applications. A finite difference method is employed to solve the governing equations of the heat and moisture exchange, which gives the outlet air properties and effectiveness for selected operating conditions for each cross-flow exchanger. Using algorithms for the HVAC supply and exhaust exchangers coupled with a run-around liquid loop, the overall effectiveness of the run-around energy recovery system is shown to be dependent on the flow rate of both the pumped fluid and each airflow, the size and design of each exchanger, and the inlet operating conditions. It is shown that an overall effectiveness of 70% can be achieved when the run-around exchanger sizes and operating conditions are correctly chosen.