Characteristics of a semicircular heat exchanger used in a water heated condenser pump
- Authors: Da Veiga, Willem Richter
- Date: 2009-02-26T12:17:42Z
- Subjects: Heat exchangers , Heat pumps , Heat transmission , Nusselt number
- Type: Thesis
- Identifier: uj:8151 , http://hdl.handle.net/10210/2158
- Description: D.Ing. , According to literature 6% of South Africa’s primary energy consumption could be saved if heat pumps were used to their full technical potential. Although there is world-wide interest in the use of heat pumps and considerable effort has been expended on heat-pump research, heat pumps are not commonly used in South Africa. The objective of this thesis is to determine the possibility of a combined evaporator or condenser with a normal pump. This will reduce cost and space of a normal heat pump and make heat pumps economically more competitive against resistance element geysers. In order to investigate this combination research is done on semicircular heat exchangers, since this is the primary geometry of the heating channels in the condenser pump. Analyses is done experimentally on a standard 28.58 mm hard drawn copper tube, cut trough the middle, with a 1.6 mm copper plate in between to obtain a semicircular heat exchanger. Turbulent flow is investigated with the flat side of the semicircular heat exchanger being horizontal or vertical, a spiralled and a s-shape semicircular heat exchanger. In each case the heat transfer coefficient is determined with the use of the Wilson plot technique. It is found that there is a significant increase in Nusselt number for semicircular heat exchangers above a normal tube-in-tube heat exchanger but the pressure loss coefficient increase with an equal amount.
- Full Text:
- Authors: Da Veiga, Willem Richter
- Date: 2009-02-26T12:17:42Z
- Subjects: Heat exchangers , Heat pumps , Heat transmission , Nusselt number
- Type: Thesis
- Identifier: uj:8151 , http://hdl.handle.net/10210/2158
- Description: D.Ing. , According to literature 6% of South Africa’s primary energy consumption could be saved if heat pumps were used to their full technical potential. Although there is world-wide interest in the use of heat pumps and considerable effort has been expended on heat-pump research, heat pumps are not commonly used in South Africa. The objective of this thesis is to determine the possibility of a combined evaporator or condenser with a normal pump. This will reduce cost and space of a normal heat pump and make heat pumps economically more competitive against resistance element geysers. In order to investigate this combination research is done on semicircular heat exchangers, since this is the primary geometry of the heating channels in the condenser pump. Analyses is done experimentally on a standard 28.58 mm hard drawn copper tube, cut trough the middle, with a 1.6 mm copper plate in between to obtain a semicircular heat exchanger. Turbulent flow is investigated with the flat side of the semicircular heat exchanger being horizontal or vertical, a spiralled and a s-shape semicircular heat exchanger. In each case the heat transfer coefficient is determined with the use of the Wilson plot technique. It is found that there is a significant increase in Nusselt number for semicircular heat exchangers above a normal tube-in-tube heat exchanger but the pressure loss coefficient increase with an equal amount.
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Heat transfer coefficient of a snow bag
- Authors: Da Veiga, Willem Richter
- Date: 2014-09-10
- Subjects: Heat - Transmission , Dry ice , Refrigerated transport , Snow bag
- Type: Thesis
- Identifier: uj:12226 , http://hdl.handle.net/10210/11993
- Description: M.Ing. (Mechanical Engineering) , In snow shooting, pressurised liquid carbon dioxide is injected via a lance into a permeable snow bag mounted near the ceiling of an insulated transport container. The decrease in pressure causes the liquid carbon dioxide to convert to "snow" and vapour inside the snow bag. The snow bag acts as a phase separator, allowing the sublimated snow to cool down the products inside a container. In this thesis the heat transfer coefficients of such a snow bag were determined experimentally and theoretically. It was found, that on average the measured heat transfer coefficient was 31% lower than the theoretical prediction. The theoretical model was used to correlate the experimental heat transfer coefficient as function of snow height. With this correlation it was possible to predict the time of the snow life to within 24%.
- Full Text:
- Authors: Da Veiga, Willem Richter
- Date: 2014-09-10
- Subjects: Heat - Transmission , Dry ice , Refrigerated transport , Snow bag
- Type: Thesis
- Identifier: uj:12226 , http://hdl.handle.net/10210/11993
- Description: M.Ing. (Mechanical Engineering) , In snow shooting, pressurised liquid carbon dioxide is injected via a lance into a permeable snow bag mounted near the ceiling of an insulated transport container. The decrease in pressure causes the liquid carbon dioxide to convert to "snow" and vapour inside the snow bag. The snow bag acts as a phase separator, allowing the sublimated snow to cool down the products inside a container. In this thesis the heat transfer coefficients of such a snow bag were determined experimentally and theoretically. It was found, that on average the measured heat transfer coefficient was 31% lower than the theoretical prediction. The theoretical model was used to correlate the experimental heat transfer coefficient as function of snow height. With this correlation it was possible to predict the time of the snow life to within 24%.
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