John Missenden

The investigation of cooling tower packing in various arrangements

The effect of form with corrugated packing on mass transfer and pressure drop characteristics in atmospheric cooling towers has been studied experimentally. The results showed that the mass transfer coefficient decreased with increase in packing pitch and increase in the ratio of rib pitch to rib height. Friction factors were expressed by a dimensional equation which included pitch and distance between the packings, for both smooth and rough surfaces. From these results, the relationship between packing mass transfer coefficient and pressure drop was deduced. The correlations were verified with additional experimental data taken with 1.1<P/D<1.70 and 1⩽p/e⩽5. This provides a useful semi-experimental relation, in an area generally lacking in design and performance data.

Cooling tower : an energy conservation resource

In this paper an investigation is made using measurements of the mass transfer rates and pressure drops for a comprehensive range of PVC plastic packings producing an economic comparison to find the best geometry and range. In order to do this, mass transfer and pressure drop for turbulent conditions in fills used in the modern cooling tower have been studied. A new method of comparison of existing cooling tower fills has been developed and the performance of the best packing has been expressed in relation to the ideal packing.

A review of research concerning the use of PCMS in air conditioning and refrigeration engineering

Publisher Summary Phase Change Materials (PCMs), which are an alternative to sensible storage, are finding new inroads into the large air conditioning scheme applications. Several novel methods of applying phase change materials in cooling systems are employed to improve the energy saving potential of PCMs. This chapter presents a scheme where thermal storage is incorporated into the cooling tower circuit that enables the system to charge the thermal store at night when there are lower wet bulb temperatures. The stored cold energy is released into the heat rejection circuit during the day, which produces lower condensing temperatures and higher efficiency. This method can reduce both peak energy and power use by as much as 35%. The chapter also discusses a scheme that uses night sky radiant cooling within the heat rejection water circuit. The lower effective temperature of the night sky is used as a heat sink with long wave radiation taking place between the condenser water and the night sky. With the use of thermal storage cold energy can be released during daytime hours to improve energy efficiency.

Analysis of the expansion valves used for controlling refrigerant feed into delicatessen cabinets in supermarkets

Abstract Delicatessen cabinets can be found in most supermarkets and are used to retail and display unwrapped chilled foods, including fresh and cooked meats, salads and pies. High operating costs for these cabinets have been regularly reported and this is mainly due to evaporation losses which occurs whilst unwrapped food is on display. One of main reasons for this has been cited to be low humidity within the display area, however, the cause of this is not clear. The role of the expansion device in the poor performance of the delicatessen cabinet is examined in this paper. This includes the results from a practical and theoretical investigation into the behaviour of thermostatic expansion valves (TEV) in the delicatessen cabinet. This showed standard expansion valve designs to be unstable and to constrain the level of humidity achieved in the display area. Alternative expansion devices are reviewed and the performance of the short tube restrictor device modelled. This has shown that this device will overcome the shortcomings of the traditional expansion devices and will significantly reduce the operating costs of the delicatessen cabinet.