Ian W. Eames

A review of adsorbents and adsorbates in solid-vapour adsorption heat pump systems

Abstract World-wide efforts to use solid–vapour adsorption technology for heat pumps have been intensified since the imposition of international restrictions on production and use of chlorofluorocarbons. Yet, to this date solid–vapour refrigeration and heat pump systems are still under laboratory testing stages. Promising recent developments in Japan, Europe and the U.S.A. include the use of porous metal hydrides and composite adsorbents. A review of adsorbents and adsorbates used in various investigations on solid–vapour adsorption heat pumps are presented in this paper, with an aim of initiating a novel concept experimental investigation.

A small capacity steam-ejector refrigerator: experimental investigation of a system using ejector with movable primary nozzle

Abstract This paper describes an experimental study of a steam-ejector refrigerator using an ejector with a primary nozzle that could be moved axially within the mixing chamber section. The effects on coefficient of performance and cooling capacity produced by adjusting the position of the nozzle were studied. The experimental rig and method are described and results are presented which clearly show the benefit of using such a primary nozzle.

Performance characteristics of HCFC-123 ejector refrigeration cycles

Ejector refrigeration systems can use low grade thermal energy, at temperatures as low as 60°C, to provide space cooling. Since this waste energy is widely available and the cost of its supply is negligible in many cases, cooling costs can be lower than conventional systems, which makes the method very attractive. The present study describes a computer simulation model for ejector refrigeration systems that was developed using an existing ejector theory. This model allows for internal irreversibilities within the ejector to be included and caters for the addition of a regenerator and a precooler for improving the system coefficient of performance. The study shows that HCFC-123 is a suitable replacement for CFC-11 in this application. Results also indicate that the use of a variable geometry ejector can maintain the optimum performance of refrigeration systems when operating conditions change.

Evaluation of a novel combined ejector-absorption refrigeration cycle — I: computer simulation

Abstract This paper describes a novel refrigeration cycle based on the combination of an absorption cycle with an ejector refrigeration cycle. The combination brings together the advantages of absorption and ejector refrigeration systems and provides high COP for refrigeration and air-conditioning. The combined cycle is particularly suitable for utilising waste thermal energy. A computer simulation program was developed for the combined cycle and used to determine the performance of the system using LiBrH2O for various generator, condenser and evaporator temperatures. Optimum operating conditions and ejector design data are also provided.

Freezing and melting of water in spherical enclosures of the type used in thermal (ice) storage systems

Abstract This paper describes and evaluates the results of an experimental study aimed at the characterisation of the freezing and melting processes for water contained in spherical elements of the type often found in the beds of thermal (ice) storage systems used building air conditioning systems. The results include semi-empirical equations that allow the mass of ice within a sphere to be predicted at any time during the freezing or melting processes. It is believed that these equations will be useful in modelling the dynamic behaviour of thermal (ice) storage using spherical elements as phase change. The apparatus, method and results are described. A novel method which was used to measure the water–ice interface position during the freezing process is also described. Several interesting results were obtained from this study.

A new prescription for the design of supersonic jet-pumps: the constant rate of momentum change method

Abstract This paper describes and evaluates a theoretical study into a new method for designing jet-pumps of the type used in jet-pump cycle refrigerators. The method assumes a constant rate of momentum change within the diffuser passage of a supersonic jet-pump. Theoretical results described in this paper indicate a significant improvements in both entrainment ratio ( R m ), and pressure lift ratio ( P DE / P s ), above those achievable from jet-pumps designed using conventional methods. Experimental data are also presented that supports the theoretical findings.

Innovations in vapour-absorption cycles

During the past decade, there has been unprecedented research interest in vapour-absorption cycle refrigeration and heat pumping driven by the need to reduce CO2 emissions related to process and comfort cooling. This paper reviews some recent innovations in vapour absorption-cycle technology, with particular emphasis on the cycle design and fluid selection. The operation and design of innovative cycles are described as well as the latest research in working fluids.

Experimental investigation of a combined ejector‐absorption refrigerator

This paper describes an experimental study of a novel heat-operated refrigeration cycle, ‘combined ejector-absorption refrigeration cycle’. In this novel cycle, an ejector was placed between a generator and a condenser of a conventional single-effect absorption refrigerator. The high-pressure vapour refrigerant produced in the generator section was used as the motive fluid for the ejector which entrained low-pressure refrigerant vapour from the evaporator and discharged it to the condenser. This was shown to significantly increase the cooling capacity and COP of the novel refrigerator above that of a conventional absorption unit with little increase in system complexity.

A novel absorption-recompression refrigeration cycle

Abstract This paper reports on a novel ejector boosted single–effect absorption-recompression refrigeration cycle. In this cycle, a steam generator, ejector and a concentrator replace the high and low pressure generators (concentrators) used in conventional double-effect absorption cycle machines, to re-concentrate the absorbent solution. The ejector here acts like a heat-pump to enhance the concentration process by increasing the flow of leaving vapour and by increasing the quantity of heat input at the concentrator. The paper provides a qualitative and quantitative description of the novel cycle and discusses design choices that lead to optimum matching of the absorbent concentrator and ejector. The important role the ejector plays in this novel refrigeration cycle is discussed and some experimental data are presented. An experimental lithium bromide refrigerator based on this cycle is described.

An experimental investigation of steam ejectors for applications in jet-pump refrigerators powered by low-grade heat

Abstract The jet-pump refrigerator cycle offers a low-capital-cost solution for utilizing low-grade waste heat in the production of cooling for buildings and process refrigeration. The heart of the jet-pump refrigerator is an ejector, the performance of which strongly determines the thermal efficiency of the cycle. This paper describes and evaluates the results of an experimental investigation into the operation of ejectors primarily for use in jet-pump refrigerators. The construction of a steam-steam ejector test facility and experimental method are described. Experimental results are provided concerning the effects of primary nozzle exit position within the mixing-entrainment section, primary nozzle exit and diffuser throat areas. The causes and effects of flow instability under conditions of high secondary pressure ratio are also discussed and methods of increasing the critical condenser pressure are identified and rated in order of effect.