Modeling and Experimental Validation of a Low-Lift, Vapor Compression Heat Pump

  • Muhammad Tauha Ali

Student thesis: Master's Thesis

Abstract

In this study, a heat pump test stand and a test chamber have been built for assessment of the energy savings of low-lift radiant-cooling cooling technology with pre-cooling control. The heat pump test stand has been built from a conventional split unit heat pump to be able to operate in either Direct Expansion (DX) mode or Chiller mode. A central data acquisition and control system has been developed for controlling compressor speed, condenser fan speed and expansion valve position. Component models have been developed from first principles to model the performance of the heat pump in DX mode or Chiller mode. The objective of this study is to present a system model based on first principles with minimum parameters estimation. The system model is found to accurately predict the system COP within ±20% for both Chiller mode and DX mode operation for majority of data points. Assessment of the effect of refrigerant oil on heat pump performance is also provided. The refrigerant oil tends to increase heat transfer in the fan-coil condenser and brazed-plate evaporator. However, at low refrigerant flow rates, the heat transfer was found to decrease for fan-coil condenser. The pressure drop was found to increase in the heat exchangers with inclusion of oil. A comparison between the component models developed in this study and those presented in (Zakula, 2010) is also given. The models developed in this study provide better estimation of system parameters especially for pressure drop. Equations for controlling condenser and compressor fan speeds during pre-cooling control for optimal operation based on the optimization results presented in (Zakula, 2010) are also presented for use in pre-cooling control.
Date of Award2011
Original languageAmerican English
SupervisorPeter Armstrong (Supervisor)

Keywords

  • Heat Pumps

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