Optimization and Process Improvements of a High Temperature Heat Pump Using Butane as Working Fluid
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With the ability to recover waste heat from industrial processes there is a huge potential to reduce the ever increasing requirement for energy. Globally industry consumes over half of the energy used, and large part of this energy is demanded at high temperature. Industrial waste heat is often at too low temperature to be used effectively, due to high temperature demands in industrial processes. With industrial heat pump system waste heat can be recovered efficiently to create high quality heat. Using the waste heat the required amount of primary energy is reduced, which reduces the environmental impact of the heat production. In this thesis a transcritical high temperature industrial heat pump is examined. A simulation of the heat pump is made in MatLab. The simulation is examined in a variety of working conditions such as: reduced supply water flow rate, variation of suction superheat and variation of discharge pressure in the transcritical area. The theoretical performance of the system is evaluated. It is found that the system is able to achieve the goal of delivering above 300 kW of heat when heating oil from 80\degree C to 160\degree C, while working at a COP of 4. It is further shown that heating up to 180\degree C is within the capacity of the system. Butane, a natural refrigerant, is used as the working fluid. The largest improvement in performance is found when reducing the compressor rpm to 90\% due to a large reduction in the compressor friction loss. At 90\% rpm a COP of 4.7 is achieved, but at the expense of reduced butane flow rate and reduced amount of produced heat. The system is further adapted with an ejector. With the ejector implemented it is found that the system may achieve a theoretical COP of 4.7 while being able to deliver a large amount of heat.