This paper presents a new method to calculate heat and mass transfer coefficients applicable to the vertical tube or plate type absorber of absorption refrigeration system. Conventional method for calculating the coefficients using logarithmic mean temperature/ concentration differences is criticized for its lacking in the theoretical rationality and usually giving untrue values except some limited situations such that temperature of the solution can be assumed to change linearly along the heat transfer surface. The newly introduced method, which is intended to overcome this difficulty, is verified by numerical simulation and is accompanied by an example applied to the experimental results.

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A two-dimensional liquid film model of LiBr solution falling along absorber cylinders has been studied to obtain boundary conditions for computing vapor flow in the absorber-evaporator of an absorption chiller. The model was established based on the assumptions that LiBr concentration and temperature profiles in the liquid film obey the third order polynomial expressions. It was indicated that mass flux and absorbed heat on the liquid surface can be calculated with simple numerical computations on the present analytical model. The overall heat transfer coefficient and total absorbed mass per second calculated with the present liquid film model was compared with experimental data for validation. The results calculated with the present model showed good agreement with the experimental data. Then, it was concluded the present model was useful enough for determining surface conditions on the LiBr liquid film around absorber cylinders.

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Absorption refrigerators available today are designed and commercialized on the basis of empirical technology. So the absorption phenomenon and heat transfer process in a conventional absorber of horizontal smooth tubes type have not been clarified yet. In the present study, a prototype experimental absorber which enables us to observe a falling film of aqueous lithium bromide on the tubes in its optically was manufactured. The absorber consists of 13 horizontal smooth tubes. And absorption experiments were carried out with a use of n-octanol as a surfactant ranging from 0 to 500ppm. Behaviors of a solution flow both on the horizontal tubes and in the space among them were observed by using a high speed video camera. Moreover, temperature distributions of the falling film of aqueous lithium bromide, cooling water and heat transfer tubes' surfaces were measured minutely. The ratios of wettability of tubes' surface were estimated, and heat transfer values on the absorber were evaluated. The refrigerating capacity increases to double with increasing surfactant concentration until its solubility limit .And it was revealed that the enhancement of refrigerating capacity with addition of the surfactant is mainly caused by a spread of wet surface of tubes.

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Absorption experiments were conducted to investigate an effect of tube pitch for a conventional horizontal smooth copper tubes type absorber. A test absorber that consists of 9 horizontal smooth tubes was built. Each tube had an outside diameter of 15.9mm and a length of 0.2m. Also, the absorber can be changed its tube pitch from 16.0mm to 31.7mm. N-octanol was used as a surfactant. Temperature distributions of a falling film of aqueous lithium bromide, cooling water and heat transfer tubes' surfaces were measured minutely. And, the behaviors of the solution flow both on the horizontal tubes and in the space among them were observed by using a high speed video camera. With measured data, refrigerating capacity, overall heat transfer coefficient, temperature effectiveness and absorption effectiveness were determined. The results showed the refrigerating capacity increased with decreasing the tube pitch. And, real overall heat transfer coefficients of the tube bundle were determined by using the local temperature distributions at the tube bundle. They became 50% larger than that of conventional calculation method. Consequently, it was conc1uded that the full contact arrangement of the smooth tubes is the best feature of the conventional horizontal tube type absorber.

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The absorption refrigerant cycle has been used in Japan, as energy shortage problem is more and more serious and environmental protection is of increasing importance. This type of air conditioner and chiller consume less electric power input than the electric one. However, the absorption refrigerator of large cooling capacity consumes some electric power with the required facility. Then in this research, the absorption cycle without the electric solution pump is proposed using a capillary pump and the possibility of making this cycle running using LiBr solution as a working fluid is investigated. As a result, it was found that the absorption cycle could be reached using a capillary wick in the generator to circulate the refrigerant and kept the strong and weak solution low pressure.

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Prevention of the global warming has called for a great necessity for energy saving. This applies to the improvement of the COP of absorption chiller-heaters. We started the development of the high efficiency gas-fired double-effect absorption chiller-heater using LiBr-H₂O to achieve target performance in short or middle term. To maintain marketability, the volume of the high efficiency machine has been set below the equal to the conventional machine. The absorption cycle technology for improving the COP and the element technology for downsizing the machine is necessary in this development. In this study, the former is investigated. In this report, first of all the target performance has been set at cooling COP of 1.35(on HHV), which is 0.35 higher than the COP of 1.0 for conventional machines in the market. This COP of 1.35 is practically close to the maximum limit achievable by double-effect absorption chiller-heater. Next, the design condition of each element to achieve the target performance and the effect of each mean to improve the COP are investigated. Moreover, as a result of comparing the various flows(series, parallel, reverse)to which the each mean is applied, it has been found the optimum cycle is the parallel flow.

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In this paper, four kinds of hybrid cycles which combined the single-stage absorption refrigerating machine and four kinds of absorption heat transformers were proposed. It is possible that each of these hybrid cycles gets high temperature and low temperature from one cycle, simultaneously. As basic cycle of absorption heat transformer, the following were chosen: two kinds of single-stage absorption heat transformer and two kinds of two-stage absorption heat transformer. As a working medium-absorbent system, H₂O-LiBr system, H₂O-LiBr-LiNO₃ system, H₂O-LiBr-LiNO₃-LiCl system, H₂O-LiBr-C₂H₆O₂ system and H₂O-LiNO₃-LiCl system were adopted. Using these five kinds of working medium-absorbent system, the performance characteristics of four kinds of hybrid cycle were simulated. And the performance characteristics of these cycles were compared.

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In this paper, four kinds of absorption hybrid cycle which introduced the compressor in the absorption cycle were proposed. As basic cycle of absorption refrigerating machine, the following were chosen: two kinds of single-stage absorption refrigerating machine and two kinds of double effect absorption refrigerating machine. As a working medium-absorbent system, NH₃-H₂O system, C₂H₅NH₂-H₂O system and C₂H₅NH₂-H₂O-LiBr system were adopted. Using these three kinds of working medium-absorbent system, the performance characteristics of four kinds of absorption hybrid cycle were simulated. And the performance characteristics of these cycles were compared.

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Fuel cells are emerging as a major power generation system that is suitable for distributed power generation from a view point of high efficiency and low pollutant emission, In order to develop high efficiency system, it is indispensable to take into consideration effective use of waste heat recovered from power generation unit. And the system design that is based on the characteristics of individual component and all of the system is significant. In this report, characteristics of phosphoric acid fuel cell (PAFC) cogeneration system, especially waste heat recovery from PAFC cell stack and exhaust gas is discussed, and operation of absorption refrigerator using waste heat of PAFC are investigated. PAFC cogeneration test facility is constructed, power generation and waste heat recovery experiment is carried out, and system performance is evaluated, As a result, beneficial knowledge are obtained as follows: It is clarified that the cell stack waste heat is dominant for the exhaust gas heat recovery characteristics, and the cooling performance of absorption refrigerator in partial load operation of PAFC. And, the effect of cooling water temperature on the performance of waste heat recovery and absorption refrigerator is obtained.

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Absorption refrigerator driven by waste heat can realize the energy savings. But if only waste heat is used as a heat source, the surplus of the waste heat or the shortage of the cooling capacity occur due to the change of the cooling capacity or the waste heat. In these cases, it is effective to back up this refrigerator with that driven by the stable source such as motive power. But using two refrigerators costs too much. This research suggests the WMVR hybrid refrigerator which can be operated using motive power and waste heat simultaneously. For this refrigerator, the simulation model was constructed and detailed characteristics were clarified. And based on these results, the effect of the design parameters such as the solution concentration and the pressure in the MVR generator on COP was revealed.

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We developed an Adsorption Heat Pump (AHP) system, which applies silica-gel as adsorbent and H₂O as refrigerant, and is possibly intended to use low temperature hot water (333K) as a driving force. The growing importance to save energy, leads us to develop energy saving systems such as Co-generation systems, including fuel cell system. It is important to use low temperature hot water in order to achieve high efficiency in total. It is, however, noticed that the lower water temperature is, the more difficult its' heat recovery becomes. We reported experimental results of the AHP system, and estimated the possibility to apply low temperature hot water from fuel cell system to the AHP system. We showed quantitatively that the AHP system is able to be driven by low temperature hot water(333K).

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Numerical analyses were made on simultaneous heat and mass transfer in packed beds of silica gel A adsorbing steam, based on a physical model taking account of elemental processes which take place in the bed. Calculations of the amount of adsorbed water from the beginning of adsorption process were in good agreement with measurements. Differences of calculated amount of adsorbed water between the physical model and a simplified model were clarified. This simplified model neglects a resistance to mass transfer in the interstices of adsorbent particles, and it treats local pressure as a constant that is equal to vapour pressure on the bed. These differences inc1eased with bed thickness, because pressure drop through the bed inc1eased. It was found that this simplicity was appropriate for thin bed, below a bed thickness of 10 mm, because of the differences were less than amount of adsorbed water of 0.5%. Equation, which gave approximate value of local pressure, was proposed. It was based on the calculated data and depended on the bed thickness. It was confirmed that the application of this equation to the simplified model gave more correct calculations. This equation is useful in predicting amount of adsorbed water.

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A conventional adsorption chiller with silica gel as adsorbent and water as adsorbate has been analyzed numerically. In the present study, a non-dimensional simulation model has been presented and a set of non-dimensional parameters for conventional adsorption chiller has been derived. The results obtained by simulation method are confirmed by the experimental results. Simulation results show that switching speed is most influential parameter and there is an optimum switching speed for cooling capacity and COP. Results also show that system performance (cooling capacity and COP) is strongly affected by the number of transfer unit of adsorber/desorber, NTUa due to severe sensible heating/cooling requirements. The model is somewhat sensitive to the number of transfer unit of evaporator, NTUe. The number of transfer unit of condenser, NTUc is the least sensitive parameter. Finally, an investigation is made parametrically to obtain the optimum value of switching speed and the number of transfer unit, NTU of different component. The present model can be employed to analyze and to optimize the adsorption cooling/heat pump system.

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This paper describes the water vapor desorption characteristics of honeycomb shape type sorbent element containing new organic sorbent of the bridged complex of sodium polyacrylate. The transient experiments in which the dry air was passed into the honeycomb type sorbent element sorbed water vapor were carried out under various conditions of air velocity, temperature, relative humidity and honeycomb length. The obtained data for desorption process were compared with those for sorption process. Finally, Sherwood number of mass transfer of the organic sorbent for desorption process was derived in terms of Reynolds number, modified Stefan number and non-dimensional honeycomb length.

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This paper has dealt with water vapor desorption characteristics of powder type organic sorbent in an air fluidized bed. The Powder type organic sorbent was fluidized in a rectangular vessel by a humid air flow. The desorption rate of vapor and the variation in temperature in the sorbent bed were measured under various air temperature and humidity conditions. It was found that the air pressure loss of the fluidized sorbent layer increased with in an increase in water vapor concentration. Finally Sherwood number for mass transfer was correlated by means of Reynolds number,modified Stefan number. The ratio of sorbent particle diameter to the fluidized bed height and Schmidt number.

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Due to the global environmental problems, the usage of natural refrigerants, such as water, ammonia, and hydrocarbons, are examined widely. Especially, absorption heat pump system using ammonia and water is penetrated widely for residential use in the U.S. and Europe, because it is easy to make the air-cooled system and to perform with high COP for heating. Authors have been developing an ammonia/water heat pump system for residential use. This system is driven by natural gas and supplies chilled water for cooling and hot water for heating. The results of performance tests indicated 6.8kW for cooling capacity and 10.3kW for heating capacity. And, some indexes which were related the charge of ammonium and the weight of the out-door unit, were compared with the same item of other equipments, such as, gas-fired LiBr absorption air-conditioners and gas engine driven heat pumps for residential use. The objective of this paper is to introduce the specifications and performance test results of the latest model, and to evaluate the performance of this heat pump system.

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Conceptual design for a free-piston Vuilleumier cycle heat pump machine was proposed. The machine was designed based upon the numerical results of a dynamic analysis method. The method included the effect of self excitation vibration with dissipation caused by the flow friction of an oscillating working gas flow and solid friction of seals. It was found that the design values of reciprocating masses and spring constants proposed in published papers related to this study were suitable for practical use. The fundamental effects of heat exchanger elements on dynamic behaviors of the machine were clarified. It has been pointed out that some improvements were required for thermodynamic analysis of heat exchangers and working spaces.

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Stirling engines have many unique advantages including higher thermal efficiencies, preferable exhaust gas characteristics, multi-fuel usage, and low noise and vibration. On the other hand, heat pump systems are very attractive for space heating and cooling, and industrial usage. There are several environmental merits of Stirling driven vapor compression (SDVC) systems. A design method for the SDVC, which is based on mathematical methods for Stirling and Ranking cycles, has been developed. The attractive SDVC performance using conventional and alternative refrigerants was shown. From the calculated Total Equivalent Warming Impact (TEWI) and operating costs, it became clear that the SDVC system with the alternative refrigerant has a higher potential as the future air-conditioning system.

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Stirling cycle system is expected as a gentle system to the earth, because the working fluid is completely free from chlorine molecules. A regenerator is the most important element of the Stirling cycle system for the performances. Flow in a regenerator is very complicated because the regenerator is made of matrix. So we are studying about Stirling cycle systems, especially the regenerator for a personal Stirling refrigerator. In this report, flow in a regenerator for a personal Stirling refrigerators is studied by using an original experimental set-up. Flow velocities and pressures at the outside of a matrix in a regenerator were measured in a round pipe. Flow effects of inlet or outlet shape and area for a regenerator were examined in detail. Pressure loss were measured at sides of a regenerator and friction factors were expressed as empirical formulas for each conditions of inlet shape of regenerator or matrixes.

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A prototype Stirling cycle refrigerator employing helium as a working fluid has been investigated to see whether the freon free machine be a viable alternative for the current household refrigerator. The prototype is a kinematics drive, and β type Stirling cycle machine of 100W refrigeration. The performance was evaluated as a function of cooling head temperature, mean pressure, frequency, and cooling capacity. The prototype has achieved the targeted refrigeration of 100W, and the COP of 1.02 under the design operation condition; 16.7Hz frequency and 0.7MPa helium pressure. The performance data was compared with the predicted ones, which was obtained by the 3rd order computational method. It has been demonstrated that the performance is in a good agreement with the predicted in the whole range of operation condition.

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In this paper, an attempt by mixing the carbon fiber into the MH bed was discussed, to enhance the heat transfer performance of the pure MH bed heat exchanger. In order to clarify the mixing effect of the carbon fiber, the effective thermal conductivity of MH bed with and without carbon fiber were measured using an unsteady state method and compared. As the best result, 3 mass % mixing carbon fiber data exhibited 4 times larger than those of the pure MH bed. Finally, after the simple refrigerator model was arranged and the influence of adding the carbon fiber on the real refrigeration effect was analyzed by using a numerical calculation.

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