A dairy refrigeration heat recovery unit and its effects on refrigeration operation |
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| Institution: | 1. Agricultural Engineering Department, Massey University, Palmerston North, New Zealand;1. Department of Nutrition, Faculty of Healthcare, Kiryu University, 606-7 Kasakake Azami, Midori, Gunma, 379-2392, Japan;2. Division of Molecular Science, Graduate School of Science and Technology, Gunma University, 1-5-1Tenjin, Kiryu, Gunma, 376-8515, Japan;3. Gunma University Center for Food Science and Wellness, 4-2 Aramaki, Maebashi, Gunma, 371-8510, Japan;1. Department of Food Technology, University of Lleida – Agrotecno Center, Rovira Roure 191, 25198, Lleida, Spain;2. Tecnologico de Monterrey, Escuela de Ingeniería y Ciencias, Centro de Biotecnología, FEMSA, Av. Eugenio Garza Sada 2501, Col. Tecnológico, 64849, Monterrey, NL, Mexico;1. Departamento de Ingeniería Química y de Materiales, Facultad de CC. Químicas, Universidad Complutense de Madrid, 28040 Madrid, Spain;2. Scintillon Institute, San Diego, CA, USA;3. Departamento de Química Analítica, Facultad de CC. Químicas, Universidad Complutense de Madrid, 28040 Madrid, Spain;1. PhD Research Scholar, Dairy Engineering Section, Southern Regional Station, ICAR-National Dairy Research Institute, Bengaluru, Karnataka, 560030, India;2. Principal Scientist, Dairy Engineering Section, Southern Regional Station, ICAR-National Dairy Research Institute, Bengaluru, Karnataka, 560030, India;1. Technische Hochschule Ingolstadt, Institute of new Energy Systems, Esplanade 10, 85049 Ingolstadt, Germany;2. Piller Blowers & Compressors GmbH, Nienhagener Str. 6, 37186 Moringen, Germany;3. Limon GmbH, Große Rosenstraße 21, 34117 Kassel, Germany;4. Universität Kassel, Dep. Umweltgerechte Produkte und Prozesse, Kurt-Wolters-Straße 3, 34125 Kassel, Germany;5. Sustainable Process Integration Laboratory – SPIL, NETME Centre, Faculty of Mechanical Engineering, Brno University of Technology - VUT Brno, Technická 2896/2, 616 69 Brno, Czech Republic;6. Energy Research Centre, School of Engineering, University of Waikato, Private Bag, 3105 Hamilton, New Zealand |
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| Abstract: | Concern about increased energy costs prompted an investigation into refrigeration heat recovery as one conservation alternative for reducing water heating costs on farm dairies. A theoretical energy balance was conducted, from which the potential for recovery of refrigeration condenser heat was estimated to be up to 60% of the water heating energy requirements.Preliminary tests with heat exchangers led to the development and testing of a tube-in-tube, counter flow heat exchanger, with fins on the refrigerant side and cores on the water side to improve the heat transfer characteristics. The exchanger, designed to provide 300 l of water at 60°C from a 2·25 kW refrigeration system which cooled 2100 l of milk per day, had a surface area on the refrigerant side of 0·84 m2, and an overall thermal conductance of 750 W m−2 °C−1. It was inserted between the compressor and the condenser of the refrigeration plant and tested with two condensing systems (air and water), together with varying conditions of condenser pressure and milk temperatures at inlet and final cooling. In addition, tests on the receiver pressure and suction superheat were performed to determine their effect on the overall system performance.Increasing the condenser pressure from 6·5 bar to 12 bar increased cooling times. In extreme circumstances the system failed to comply with the New Zealand milk cooling regulations. The average coefficient of performance (C.O.P.) of the refrigerator (with the heat exchanger in the circuit) decreased with increasing pressure, varying from 3·0 to 2·3 over this range of pressures for the water cooled condenser system. Values for the air cooled condenser system were 0·3 to 0·4 lower due to fan power consumption. |
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