Yoshinori Hamamoto

Performance evaluation of a low-temperature waste heat driven multi-bed adsorption chiller

Abstract This study aims at improving the performance of thermally activated silica gel–water adsorption refrigeration cycle by applying multi-bed scheme. In this paper, a three-bed non-regenerative silica gel–water adsorption chiller design is outlined along with the performance evaluation of the innovative chiller. The three-bed chiller will be able to work as high efficient single-stage adsorption chiller where driving source temperature is between 60 and 95 °C along with a coolant at 30 °C. The three-bed cycle comprises with three adsorber/desorber heat exchangers, one evaporator and one condenser. Waste heat or renewable energy sources will power the high temperature desorber. If two beds are in desorption mode, the hot water outlet from the lead desorber will drive the lag desorber before being released to ambient. This facilitates the maximum utilization of the waste stream. On the contrary, if two adsorber or desorber beds are in adsorption mode, the cooling water outlet from the lead adsorber will cool down the lag adsorber. In this circumstance, two adsorber beds will be connected with the evaporator and will enhance evaporation. A cycle simulation computer program is developed to analyze the influence of operating temperatures (hot and cooling water temperatures, adsorption/desorption cycle time) on cooling capacity and coefficient of performance (COP) of the innovative three-bed cycle in parallel flow configuration of the heat transfer fluids. The cycle simulation calculation indicates that the COP value of the three-bed chiller is 0.38 with a driving source temperature at 80 °C in combination with coolant inlet and chilled water inlet temperatures at 30 and 14 °C, respectively. The delivered chilled water temperature is about 6 °C with this operation condition. Simulation results also show that from the two to three beds, waste heat recovery efficiency, η is boosted by about 35%.

Heat transfer to a supercritical pressure fluid flowing in sub-bundle channels

Supercritical pressure water cooled reactor (SCWR) has been regarded as an innovative nuclear reactor. For the design and development of the SCWR, heat transfer performance under supercritical pressure is one of the most important indicators. In this paper, experimental data are presented on the heat transfer to a supercritical pressure fluid flowing vertically upward and downward in a small diameter heated tube and two sub-bundle channels with three heater rods and seven heater rods, using HCFC22 as the test fluid. Downstream of grid spacer for the sub-bundles, heat transfer enhancement was observed in the upward flow, but not in the downward flow. The enhancement was remarkable especially when the heat transfer deterioration occurs in the fully developed region unaffected by the spacer. The heat transfer correlation for the downstream region of the spacer was developed in the normal heat transfer of sub-bundles. In the fully developed region for the sub-bundle, occurrence of the heat transfer deterioration was suppressed or degree of the deterioration was moderated. At high mass velocity for downward flow in the seven rod sub-bundle, oscillation of heat transfer was observed in the region of the enthalpy over the pseudocritical point.

FUEL CELL WASTE HEAT POWERED ADSORPTION COOLING SYSTEMS

In the present paper, the effect of desorption temperature on the performance of adsorption cooling systems driven by waste heat from fuel cells was analyzed. The studied adsorption cooling systems employ activated carbon fiber (ACF) of type A-20–ethanol and RD type silica gel–water as adsorbent–refrigerant pairs. Two different temperature levels of waste heat from polymer electrolyte fuel cell (PEFC) and solid oxide fuel cell (SOFC) are used as the heat source of the adsorption cooling systems. The adsorption cycles consist of one pair of adsorption–desorption heat exchanger, a condenser and an evaporator. System performance in terms of specific cooling capacity (SCC) and coefficient of performance (COP) are determined and compared between the studied two systems. Results show that silica gel–water based adsorption cooling system is preferable for effective utilization of relatively lower temperature heat source. At relatively high temperature heat source, COP of ACF–ethanol based adsorption system shows better performance than that of silica gel–water based adsorption system.

Boiling Heat Transfer and Pressure Drop of a Refrigerant R32 Flowing in a Small Horizontal Tube

In this study, experiments were performed to examine characteristics of flow boiling heat transfer and pressure drop of a low global warming potential refrigerant R32 flowing in a horizontal copper circular tube with 1.0 mm inside diameter for the development of a high-performance heat exchanger using small-diameter tubes or minichannels for air conditioning systems. Axially local heat transfer coefficients were measured in the range of mass fluxes from 30 to 400 kg/(m2·s), qualities from 0.05 to 1.0, and heat fluxes from 2 to 24 kW/m2 at the saturation temperature of 10°C. Pressure drops were also measured in the rage of mass fluxes from 30 to 400 kg/(m2·s) and qualities from 0.05 to 0.9 at the saturation temperature of 10°C under adiabatic condition. In addition, two-phase flow patterns were observed through a sight glass fixed at the tube exit with a digital camera. The characteristics of boiling heat transfer and pressure drop were clarified based on the measurements and the comparison with data of R410A obtained previously. Also, measured heat transfer coefficients were compared with two existing correlations.

Selected Papers from the International Symposium on Innovative Materials for Processes in Energy Systems 2013 (IMPRES2013): Part II

The International Symposium on Innovative Materials for Processes in Energy Systems (IMPRES) has been held every 3 years, and this was the third conference, following the successful completion of IMPRES2007 in Kyoto, Japan, and IMPRES2010 in Singapore. IMPRES2013 was held September 4–6, 2013, at Kyushu University in Fukuoka, Japan. The theme of the conference was the application of novel materials in the field of energy systems, with a special focus on multiphase processes in various energy conversion systems. Materials for fuel cells, heat pumps, sorption systems, and various energy conversion/storage devices, among other topics, were discussed. The goal of the conference was to connect researchers focusing on different aspects of multiphase processes in energy conversion and to promote the interchange of ideas across subjects. The conference was co-organized by the International Institute for Carbon-Neutral Energy Research (WPI-I2CNER) at Kyushu University, the Advanced Graduate Program in Global Strategy for Green Asia (Green Asia, GA program) at Kyushu University, and the Division of Energy Engineering of the Society of Chemical Engineers Japan.