Heat Transfer And Pressure Drop Characteristics Of Refrigerant 42 Condensing Inside Horizontal Tubes

An investigation was conducted into the condensation of refrigerant 12 inside a horizontal tube. Following an exhaustive review of the literature a statistical comparison was carried out on previously published heat transfer and pressure drop correlations and recommendations were made as to those most appropriate for the design of commercial refrigeration condensers. An experimental apparatus was designed and fabricated, on which measurements of condensing heat transfer coefficients were made together with observations of flow regimes. Mathematical modelling techniques were used to assist in the design and commissioning of the apparatus, and a computer based data logging system was developed to monitor the apparatus and record the results. A method of correlating a wide range of condensing flow regimes is presented, based on the use of a liquid Froude number. Tested against the measured, and an independent set of data the correlation achieved a high discrimination between flow regime types. A method of correlating condensing heat transfer coefficients was developed, also based on the use of a liquid Froude number. The method although simple in application, correlated the measured data within - 20%. A computer aided condenser design programme was written incorporating the flow regime and heat transfer correlations, and was successfully tested against the measured data. An investigation was made into the use of refrigerant 12/22 mixtures in a conventional refrigeration system which incorporated a flooded type evaporator. It was not found possible to effect any power saving, but by adjusting the concentration of refrigerants it was possible to obtain a substantial variation in the plant capacity.