In air-conditioning field, a dehumidification and humidification have become increasingly important for human health and comfort. Much attention has been paid recently to a desiccant air-conditioning system as an alternative to the conventional system with a vapor compression cycle. In this paper, we focus on a liquid desiccant air-conditioning system using lithium chloride – water solution and investigate the heat and mass transfer of packed bed regenerator experimentally. In the experiment, effects of the air superficial velocity and solution mass flux on the outlet air conditions and the average overall heat and mass transfer coefficients are examined. As a result, the average overall heat and mass transfer coefficients increase with increasing of the air superficial velocity, however, the average overall heat transfer coefficient is almost constant with increasing of the solution mass flux.

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In this study, visual observation of flow pattern by using a high-speed camera and direct measurement of liquid film thickness by using a laser displacement meter for slug flow in microchannels with inner diameter of 0.5 mm, 1 mm and 2 mm were conducted. 5 fluids with different surface tension and viscosity (water, ethanol, FC72, KF-96L-0.65cs, KF-96L-2cs) were selected to investigate the effect of physical properties on the flow pattern and liquid film thickness. Experimental results were compared with several existing correlation to provide better understanding of two phase flow and heat transfer characteristics at a various tube scale and working fluid physical properties. For the flow pattern, the difference between experimental data and flow pattern map in previous studies becomes larger as the tube diameter increases, and liquid surface tension decreases. However, liquid viscosity has relatively small effect on its flow pattern. For the bubble velocity and liquid film thickness, comparing with correlations in previous studies, the error between experimental data and correlations becomes larger when liquid surface tension and viscosity are low relatively. And also in that case, as the tube diameter increases, the error becomes larger.

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Pressure loss of compressed air in discharge process decreases isentropic efficiency of a screw type compressor, because of excess compression energy for pressure loss. For this reason, we tried to reduce the pressure loss. Pressure inside a case was measured via a pressure transducer which was located in a female rotor. And discharge energy loss was estimated by analyzing a pressure diagram. The pressure loss is significantly influenced by shape of a discharge port. We examined their relation by comparing the pressure loss between three types of the discharge port with different shape of center convex. As a result, it was revealed that shortening convex of the discharge port causes decrease of discharge energy loss and degradation of volumetric efficiency. Therefore, in order to improve isentropic efficiency, the shape of center convex should be determined to minimize degradation of volumetric efficiency and to maximize decrease of discharge energy.

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The pρT properties in the liquid phase and gaseous phase include saturated vapor pressure of R 245fa (1,1,1,3,3-pentafluoropropane) were measured by metal-bellows volumometer. The measurement was carried out in the temperature range from 310 K to 410 K. As for the liquid phase, twenty nine pρT proper_-3 ties were obtain_-3 ed in the pressure range from 502 kPa to 5002 kPa and the density range from 910 kg･m to 1323 kg･m . As for the gaseous phase, forty four pρT_-3 properties wer_-3 e obtained in the pressure range from 209 kPa to2632 kPa and the density range from 12 kg･m to 184 kg･m . saturated vapor pressures were also obtained. The e_-3 xperimental un_-3 certainties are estimated to be 10 mK for temperatures, 1.7kPa for pressures, and 0.1 kg･m to 2.1 kg･m for densities. The sample purity was better than 99.80% in the mole fraction. On the basis of the pρT data, coefficients of the equation which is proposed by Sato et al. for liquid phase and virial equation for gaseous phase were obtained. From this result, the Sato equation was correlated with relative standard deviation of 0.07%. And the virial equation was correlated with relative standard deviation of 0.36%. In addition, saturated liquid density and saturated vapor density were determined by substituting the saturated vapor pressure into their equations. Then, the present data were compared with values calculated from existing equation of state.

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The present study experimentally investigated the condensation heat transfer characteristics, condensate flow modes, and condensate flooding angle of R245fa on horizontal low-finned and microscopic-grooved tubes. Seven low-finned and three microscopic-grooved tubes with tube diameters of approximately 19 mm at the fin tip were used as the test tubes. Experiments were conducted at a constant saturation temperature of 40 °C. Three condensate flow modes—droplet mode, droplet-column mode, and column mode—were observed in this experiment. The transition film Reynolds number of the condensate flow mode of the low-finned tubes was different from that of the condensate flow mode of the microscopic-grooved tubes. The condensate flow mode of the microscopic-grooved tubes transited from droplet mode to droplet-column mode had a lower film Reynolds number than that of the low-finned tubes. The condensation heat transfer characteristics of the low-finned and microscopic-grooved tubes were experimentally investigated to clarify the condensate flow modes and the effects of fin pitch, fin height, and fin geometries on the condensate flooding angle and condensation heat transfer.

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This paper proposes a three-bed three-stage adsorption cycle with a new operational strategy. The cycle consists of three adsorber/desorber heat exchangers, one evaporator, and one condenser. The two beds on the low-pressure side operate in a re-heat cycle, and another bed on the high-pressure side operates in a conventional cycle. The objectives of the current study were to evaluate the cycle at a low heat source temperature such that it can be driven by solar or waste heat and to reduce the number of heat exchangers from six beds to three beds. A simulation model was developed, and the system behavior and its performance were predicted. The performance of the proposed cycle was compared with that of a conventional six-bed three-stage adsorption cycle. The simulation results showed that the proposed cycle with the new operational strategy could operate at low heat source temperature i.e., 45 °C, and offers approximately five times higher performance in terms of SCP than the conventional cycle. Consequently, the proposed cycle is effective for use of a low-grade heat source, even with three beds.

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Solar single-double effect combined absorption chiller has come into wide use compared with other types of solar absorption system because it is equipped with high-efficient double effect apparatus of helping solar heat. This paper reports the machine design to enhance the performance by solar heat. So far, thermal conductance KAs of elements composed in absorption chillae have been often limited in machine design because the change of KAs means remanufacture of the test machine. Hence, easily to realize the machine design with the most efficient performance COP in the objected system, we evaluated the performance with KAs designed by simulation, which is a good way to evaluate system performance easily without empirical method and leads to design to save time. Each KA needs to be concluded under the conditions of common parameter, for example, evaporator temperature, condensation temperature, pinch temperatures of heat exchangers, etc. In the simulation result, it is clarified that the reverse flow type can be the highest performance among several types of single-double effect absorption cycle suggested.

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In this study, condensation and pool boiling heat transfer characteristics of R134a, R1234ze(E), R245fa and R1234ze(Z) are investigated experimentally on a horizontal plane tube. The test tube of outer diameter and heat transfer length are 19.12 mm and 400 mm, respectively. For the condensation at saturation temperatures from 20 to 60 °C and the degrees of wall subcool from 0.77 to 28.81 K, the measured condensation heat transfer coefficient of R1234ze(Z) agree with that of Nusselt's filmwise condensation theory within approximately ±11 %. The condensation heat transfer coe_o fficient of R1234ze(Z) is slightly higher than _-2 other refrigerants. For pool boiling at saturation temperatures from 10 to 60 C and heat fluxes from 0.73 to 80.13 kWm , the measured pool boiling heat transfer coefficients reasonably agree with that predicted by Stephan-Abdelsalam correlation. The pool boiling heat transfer coefficie_o nts of R1234ze(E) and R134a _-2 are significantly higher than those of R1234ze(Z) and R245fa at saturation temperature 20 C and heat flux 15 kWm . However, the pool boiling heat transfer coefficient of R1234ze(Z) becomes larger with increasing the reduced pressure.

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