Direct expansion ground source heat pumps are a technology which is actually gaining interest among scientific community. These systems operate on the well-known simple vapor compressor refrigeration cycle. The most popular heat pumps using a secondary ground loop also operate on the simple vapor compressor refrigeration cycle. The main difference between both technologies is that the ground heat exchanger is an integral component of the refrigeration cycle for the direct expansion systems. Therefore, the energetic and operational performances of the system are directly related to the working fluid behavior, the refrigerant, in relation with the diffusive ground heat transfer.
The literature review indicates that scientific researches and publications related to direct expansion ground source heat pumps are limited. Therefore, regarding experimental results as well as simulation models, the actual information available in the scientific literature is not sufficient in order to obtain a satisfactory scientific appreciation of the technology.
The main scope of the actual work is obtaining scientific experimental results regarding operational characteristics of such systems and also developing a numerical simulation model of a refrigerant-ground heat exchanger. The obtained experimental results will permit the analysis and comprehension of the complex dynamic operational characteristic of such systems, mainly regarding the refrigerant-ground heat exchanger. The simulation model developed will offer the possibility to realize parametric simulation for either the analysis or the development of refrigerant-ground heat exchanger.
The system studied in this work is an available commercial unit and has the possibility to operate in both heating and cooling mode. When used in heating mode, the refrigerantground heat exchanger is the evaporator and consists of three ground loops in parallel having their own dedicated thermostatic expansion valve. When used in cooling mode, the refrigerant-ground heat exchanger is the condenser and consists of either one or a pair of ground loops in parallel. The operational situation is controlled by the onboard computer of the unit based on an operational sequence established from the manufacturer.
The refrigerant-ground heat exchanger has the particularity to have a diffusive and transient heat transfer from the outer boundary of the refrigerant flow. The actually available models in the literature mainly solve a convective heat transfer at the outer boundary of the refrigerant flow. The development of a dynamic numerical model integrating the governing continuity, momentum and energy equations for the refrigerant fluid flow with transient ground heat transfer is a scientific contribution of the actual work.
In order to obtain scientific experimental results from the system, a test rig has been build including a detailed instrumentation. Several experimental tests have been realized to obtain results for both the heating and cooling mode. Particular tests have also been conducted in order to obtain detailed results regarding the complex and dynamic operational characteristic of the ground loops in both heating and cooling mode.
Experimental comparison of the numerical simulation model has been realized with the obtained experimental results.
| Date | 10 Aug 2011 |
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| Original language | French |
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| Awarding Institution | - École de technologie supérieure
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| Supervisor | Louis Lamarche (Supervisor) & Stanislaw Kajl (Co-supervisor) |
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Beauchamp, B. (Author),
Lamarche (Supervisor) &
Kajl (Co-supervisor),
10 Aug 2011Student thesis: Doctoral thesis › Doctorate in Engineering: Engineering