Ocean thermal energy conversion (OTEC) and discharged thermal energy conversion (DTEC) are expected to be the next generation energy production systems. Both systems use a plate type evaporator, and ammonia or ammonia/water mixture as a working fluid. It is important to clarify heat transfer characteristic for designing efficient power generation systems. Measurements of local boiling heat transfer coefficients and visualization were performed for ammonia /water mixture (z = 0.9) on a vertical flat plate heat exchanger in a range of mass flux (7.5 - 15 kg/m2s), heat flux (15 - 23 kW/m2), and pressure (0.7 - 0.9 MPa). The result shows that in the case of ammonia /water mixture, the local heat transfer coefficients increase with an increase of vapor quality and mass flux, and decrease with an increase of heat flux, and the influence of the flow pattern on the local heat transfer coefficient is observed.
In this paper, we studied a pre-cooling system by using adsorption cool storage for automobiles on the purpose of getting a cool breeze immediately after getting on. The adsorbent should be appropriate depends on the operation condition of adsorption cool storage. We found that FAPO34 is appropriate because the adsorbed amount increases at the relative humidity 0.05. We verified the effect by simulations and experiments. As results, it was proven to be able to lower the temperature of the blow air from 60°C to 35°C when the cool storage which uses absorbent 1.0kg was operated for 60 seconds before getting on.
The influence of thawing speed on denaturation of muscle protein and quality of several kinds frozen fish meat was studied by measuring Ca-ATPase activity, drip loss, and microscopic observation. Frozen bigeye tuna, chub mackerel, alaska pollack and yellow tail meat thawed at 10°C by air (slow thawing) and water (rapid thawing). Ca-ATPase activity of slow thawed fishes meat decreased than it of rapid thawed fishes meat. On the other hand drip loss of slow thawed fishes meat increased than it of rapid thawed fishes meat. Decreasing of Ca-ATPase activity showed a good linear relation to increasing of drip loss. Further, from microscopic observation, it was confirmed that muscle cells of slow thawed fishes meat were disrupted than it of rapid thawed samples. Therefore,it was suggested that rapid warming on thawing process is better to inhibit protein denaturation and drip loss.
During transport using refrigerated trucks, the maintaining of the recommended conditions throughout a cargo is required to preserve the quality of fresh fruit and vegetables. Temperature distribution within a refrigerated container is governed by airflow pattern with thermal transport. In this study, Computational Fluid Dynamics(CFD) predictions were used to investigate the temperature distribution within a typical refrigerated truck filled with cardboard packed eggplants. Numerical modeling of heat and mass transfer was performed using the CFX code. In order to verify the developed CFD model full-scale measurement was carried out within a load of eggplants during transport. CFD predictions show reasonable agreement with actual data.
The lubricating oil in the refrigerant flow in a CO2 heat pump system has a great influence on cycle performance. In order to measure the OCR (Oil circulation ratio), a mixing chamber and a visual vessel were installed at the outlet of the gas-cooler. By mixing the oil and refrigerant, the liquid mixture of oil and refrigerant becomes cloudy at the outlet of the gas-cooler. By measuring the infrared ray transmittance of the oil-refrigerant liquid mixture, it was found that the transmittance decreases with an increase in the oil circulation ratio. For this reason, it is found that, in spite of immiscible refrigerant and oil, the measurement of the oil circulation ratio is possible by measuring the transmittance of infrared ray at the outlet of the gas-cooler.
The air conditioning system with organic sorbent is able to utilize the low temperature waste heat. This paper has dealt with dynamic sorption of powder organic sorbent in a fluidized bed during batch cycle operation. The experiments were carried out under the various conditions such as cycle time, inlet air flow velocity, temperature of the heat exchanger, amount of sorbent. As a result, the cycle time which maximizes the amount of dehumidification became clear. The most suitable cycle time was decided by the balance of the speed of sorption reaction and the effects of heating and cooling. The heating effect and the cooling effect were controlled by the temperature of the heat exchanger. With a rise of the desorption temperature, the most suitable cycle time became short and the amount of dehumidification increased but heat efficiency dropped. On the other hand, with a rise of the sorption temperature, the amount of dehumidification decreased but this system showed an enough dehumidification performance when the sorption temperature is 30°C.
A numerical calculation method has been developed to determine the optimum thawing method for minimizing the increase of metmyoglobin content (metMb%) as an indicator of color changes in frozen tuna meat during thawing. The calculation method is configured the following two steps: a) calculation of temperature history in each part of frozen tuna meat during thawing by control volume method under the assumption of one-dimensional heat transfer, and b) calculation of metMb% based on the combination of calculated temperature history, Arrenius equation and the first-order reaction equation for the increase rate of metMb%. Thawing experiments for measuring temperature history of frozen tuna meat were carried out under the conditions of rapid thawing and slow thawing to compare the experimental data with calculated temperature history as well as the increase of metMb%. The results were coincident with the experimental data. The proposed simulation method would be useful for predicting the optimum thawing conditions in terms of metMb%.