Air-cycle System Research Articles

Feasibility of air cycle systems for low-temperature refrigeration applications with heat recovery

In this paper the viability of an air cycle refrigeration system (Joule cycle) is investigated for a moderately low-temperature cooling system with heat recovery. The goal is to determine the best possible cycle configuration of heat exchangers and turbomachinery components for this particular application, and then to determine whether it can compete with a conventional vapour compression system. Simple models were developed for each cycle configuration, and the results were compared with each other on a consistent basis. The sensitivity of the system to heat exchanger effectiveness and expander and compressor efficiency was determined, and contours were plotted.

究極の自然冷媒 : 空気の利用技術(<特集>自然を考えたエンジニアリング)

究極の自然冷媒 : 空気の利用技術(<特集>自然を考えたエンジニアリング)

Enhancing the performance of evaporative spray cooling in air cycle refrigeration and air conditioning technology

The phase out of CFC refrigerants and the concern over their proposed replacements, HFC, has led to a reassessment of many natural refrigeration technologies including air cycle. It is recognised that to fulfil the full potential of air cycle technology, improvements in system energy consumption must be made. One area where it is believed that significant energy savings can be made is the use of evaporative spray cooling. This paper reports preliminary results of a project aimed at investigating and enhancing the performance of evaporative spray cooling. Initially, the performance of five different types of atomiser was examined under varying operating conditions. From these tests it was possible to identify the most appropriate atomiser for the application and carry out further tests to determine the effect of other parameters such as water temperature and atomiser location. A system model has been used to interpret the findings of these tests to see how the energy performance of an actual air cycle system is affected by evaporative spray cooling. Further tests must be carried out before a definitive understanding of evaporative spray cooling is reached. These are expounded in this paper.

Cooled air cycle system and method for operating such a system

Cooled air cycle system and method for operating such a system

Environmental Systems

FROM the outset it was decided that the P.1127 cabin conditioning system should be based on the boot‐strap air cycle system. Hot air from a bleed off the engine h.p. compressor would be processed in a heat exchanger‐Cold Air Unit (C.A.U.) system and delivered, cooled and dewatered, to the cabin. For cabin heating a controlled amount of hot air would bypass the heat exchanger/cold air unit assembly and enter the main supply pipe, thus raising the air temperature the required amount. Cabin temperature control would be automatic following an initial selection by the pilot, but he would also have the facility to override the automatic control if required.

Air Conditioning in Aircraft

SummaryThe general requirements for the complete air conditioning of aircraft are discussed in the light of the complete system concept. The author takes into consideration safety, differential pressure, weight saving, power and air supply, passenger comfort, cooling and humidity. Particular systems are then described and there is a section on the test equipment required for the laboratory testing of air conditioning equipment. Cooling systems are taken first and divided into the air cycle system embodying bootstrap, turbine fan, and regenerative applications of cold air units–the vapour cycle system employing a boiling tank and that using proprietary refrigerants; properties of liquid refrigerants are discussed. Regulation of cabin temperature, air flow, humidity, pressure and oxygen is done by control systems and the equipment used is described. Four appendices give (1) suggested detailed requirements for air conditioning equipment and user requirements, (2) sample data and calculations for air conditioning a 100-seater civil transport, (3) some notes on the definition of refrigeration terms and (4) data on pressure losses in aircraft ducts.