Date of Award


Document Type

Master Thesis

Degree Name

Master of Engineering (Research)


Department of Mechanical and Manufacturing Engineering

First Advisor

Dr. S.F. Cassidy


Current environmental concerns have led to large scale research and development in the area of alternative energy supplies. The alternative energy system of interest in this study is the heat pump. Heat pumps extract heat from a variety of sources such as air, water and the earth, upgrade and transmit it to the required location. The aim of this thesis is to develop mathematical and experimental models to evaluate the performance of a heat pump which uses the earth as its thermal source. These models will then form the basis of design aids for installers sizing closed loop collection systems under Irish conditions.

In this study, a mathematical model capable of simulating the heat transfer process from the earth to the collector of a heat pump system is described. The model allows parameters such as circulating fluid flowrate, thickness of the collector wall, soil diffusivity and the thermal resistivities of the fluid, collector and soil, to be varied and their affect on heat pump performance analysed. The model determines the optimum collector length for any size of heat pump system in any type of soil.

A heat pump test facility has been built to evaluate the thermal performance of a ground loop collector. The design and commissioning of this test facility is documented in this thesis. The experimental results from the facility are compared to predicted values from the mathematical model. Good agreement was found showing that the mathematical model is capable of describing accurately heat pump performance. The overall efficiency of the test facility is compared to two other collection systems in the region. Extensive experimentation has resulted in the determination of the optimum system set-up and the feasibility of the earth as a thermal source.

The research concludes with a feasibility study that compares the capital and running costs of these systems to the more conventional methods of heating. The analysis suggests that these systems are most suitable in countries which require air conditioning. In Ireland, they are suitable in areas which require continual amounts of heat at a low temperature, circa 30°C. Such applications would include plant and animal nurseries, swimming pools and hospitals.

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