Magneto-Caloric Heat Pump for Space Heating

• Main Author: Lima, Maria Beatriz Fonseca
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2022
• Subjects: Alternative Energy; Alternative energy sources; Cold; Electromagnetics; Energy consumption; Energy resources; Energy transition; Fluid mechanics; Heat exchangers; Heat transfer; HVAC; Magnetic fields; Phase transitions; Renewable resources; Reynolds number; Thermodynamics; Water temperature
• ISBN: 9798383284049

The ever-growing subject of energy transition needs to be thought out for residential buildings, as they are responsible for a larger slice of energy consumption in the EU.Heat pumps have been increasingly the chosen technology for space heating in the last decade for their multiple benefits, from efficiency to sustainability. However, most of these devices use pollutant refrigerants that have a negative impact on the environment.Consequently, the aim of this thesis is to introduce an alternative technology to conventional vapor compression heat pumps, which is the magneto-caloric heat pump. These may be a competitive option, as they are less ecologically harmful and have potential for high efficiencies. Additionally, the work was carried out to incorporate this technology for the heating of Dutch houses. The system included the magneto-caloric heat pump, an underfloor heating system as the heat sink, and a borehole heat exchanger as the heat source.A different methodology was applied in each component. Nevertheless, all of them were implemented in Python. The magneto-caloric heat pump was modeled using the finite-difference method for time and space discretization, the Crank–Nicolson method for the conduction terms, and the implicit upwind method for the enthalpy terms. Moreover, the underfloor heating system was modeled using the NTU method for the heat transfer between the water and the pipe level, and the Crank–Nicolson method for the heat transfer between the following layers of the floor and ultimately to the room. Finally, numerical and iterative methods were applied to obtain the g-functions that would dictate the different temperatures in the borehole heat exchanger.After implementation, a maximum coefficient of performance (COP) of 6.92 was achieved for a heating season of the average temperatures that occurred hourly from 2001-2010. That heating season was considered from 15th September to 14th May of the following year. During that period, the seasonal coefficient of performance (SCOP) of the system was 6.18. It was also possible to keep the temperature inside the house within 19.8 ◦C and 20.7 ◦C. For a colder heating season, 2009-2010, heating demands rose to the maximum capacity of 3000 W. For that value, the COP was 3.91. The SCOP for this specific season was slightly lower and equal to 5.83.These COP values are possible to be obtained due to the control methods implemented, such as the implementation of intermediate heat exchangers between the heat sink and the magnetocaloric heat pump, and between the heat source and the magneto-caloric heat pump; the control of the frequency and mass flow rates in the magneto-caloric heat pump to work at the best COP for each heating demand.