With the aim of developing a method for reducing energy consumption of room air conditioners, we address a higher-efficiency design of the rotary compressor. We focused on a swing piston rotary compressor that has a small pillar at the tip of the vane and constitutes a turning-pair of vane and piston, which limits the rolling motion of the piston. By limiting piston rotation, heat transfer to the suction process from the compression chamber will be suppressed, and we can expect higher volumetric efficiency. Before investigating volumetric efficiency, we performed a dynamics analysis of the new rotary compressor and examined the forces and dynamic behavior of its components, as well as the mechanical efficiency. We realized the following results: First, by reducing the vane tip radius, the friction loss between vane and piston is reduced, and the mechanical efficiency is improved; and second, the new rotary compressor has less vane tip friction loss and, on the other hand, slightly higher friction loss between vane side and cylinder compared with the rolling-piston rotary compressor. Consequently, the new rotary compressor would have a little higher mechanical efficiency compared with rolling-piston rotary compressor.
Vapor pressure and saturated liquid density for HCFO-1233zd(E) and HCFO-1233xf were measured in the temperature range from 300 K to 400 K at intervals of 10 K by the extraction method. Experimental uncertainties are 0.028 K for temperature, 0.4～3.1 kPa for pressure and 0.9～1.4 kg‧m-3 for density. On a basis of the present data, correlations of vapor pressure and saturated liquid density were formulated as a function of temperature. The standard deviations of vapor pressure from correlations were 0.3 kPa for HCFO-1233zd(E) and 0.9 kPa for HCFO-1233xf. The standard deviations of saturated liquid density from correlations were 0.4 kg‧m-3 for HCFO-1233zd(E) and 0.2 kg‧m-3 for HCFO-1233xf.
This study was conducted to investigate the effect of tube diameter on flow pattern, boiling heat transfer, and frictional pressure drop characteristics of R32 in horizontal smooth small-diameter tubes with 3.5 and 2.2 mm inner diameter. The boiling heat transfer coefficients were measured over a range of mass velocities from 50 to 400 kg/(m 2s), over a range of heat fluxes from 5 to 20 kW/m 2, and at a saturation temperature of 15°C. The frictional pressure drop for adiabatic two-phase flow was measured over a range of mass velocities from 100 to 400 kg/(m 2s) and over a range of vapor qualities from 0.1 to 0.9. The flow patterns for adiabatic two-phase flow were observed at the exit of the test tubes for plug, wavy, and annular flows. Plug flow was observed over a wide range of vapor qualities with decreasing the tube diameter. The effect of tube diameter on the heat transfer and frictional pressure drop under low mass velocity conditions was larger than that under high mass velocity conditions.
In this study, at first, the thermal characteristics of conventional lamps such as fluorescent lamps and energy-saving lamps such as LED and CCFL were investigated experimentally to examine their effect on the air-conditioning load in business-related buildings. Then, based on the experimental results, air-conditioning loads in a mass merchandizing store with conventional fluorescent lamps or LED lamps were obtained by numerical simulations using the software “BEST.” In case of the downlight-type lighting system, the fraction of heat emission of a lamp toward the room direction to its electricity consumption was 18 - 28% in both the conventional fluorescent lamps and energy-saving LED lamps. In the straight-tube type lighting system, the fraction of heat emission was about 50% in both fluorescent lamps and LED lamps. It was found that, by replacing the fluorescent lamps with LED lamps in the store, the annual cooling load decreases while the annual heating load increases, and the maximum air-conditioning load can appear in the heating season even in buildings with large internal heat generations. This suggests the necessity of revised air-conditioning load models for buildings with energy-saving lamps.
HFC refrigerant (R32) is an environmental-friendly refrigerant compared to the existing R410A refrigerant with only one third of the global warming potential (GWP), which is generally used in developed countries. Because R32 is a mild flammable refrigerant, safety assessments are necessary to ensure the safeness of R32 air-conditioner before launching it into the market. This study presents a novel simulation method to evaluate the flammable risk in case of R32 leakage from indoor air-conditioner. Precision of this method is verified by comparing the simulation results and the experimental observation using R32 loaded actual equipment. We focused on a residential floor mounted air-conditioner model which is considered to have a higher risk of fire compared to the other household models.
Effective freezing for foods with air blast requires well-controlled air flows inside freezers. However, it is difficult to control the air flow inside the industrial spiral belt freezers due to their large volume and complicated structure. In this study, CFD (Computational Fluid Dynamics) was applied on the virtual space of a prototype testing freezer machine. Moreover, velocity on the conveyor belt of actual machine was measured in order to verify the reliability and interactivity of CFD model. As a result, CFD enabled to visualize the whole air flow pattern inside the freezer, and it was found that both analyzed and measured velocities of the air flow on the conveyor were highly correlated. It is concluded that the CFD model can be a useful tool to comprehend the behavior of air flows inside the industrial spiral belt freezer, and would realize effective development for technologies of food freezing.
Recently at commercial buildings and office buildings it is popular to install VRF (variable refrigerant flow) compression type heat pump system. Especially, VRF system which has multi indoor units is install in large building because this system has large adjusting capacity. On the other hand, depend on indoor unit’s condition the way to operation the other indoor unit change dramatically under unsteady-state driving, so it is too difficult to find optimum operating condition. In addition to changing the number of active indoor units occurs big change of quantity of refrigerant flow, refrigerant distribution changes step by step. We make the numerical simulation model which can be evaluate unsteady-state driving and make sure the accuracy of model, compared test results, and we analyze the effect of the case of decreasing active indoor unit.
Air temperature distribution in an adsorbent desiccant rotor was measured for visualization of simultaneous heat and mass transfer in the rotor. Interpretation of the temperature distributions was carried out. At first, temperature distribution in a desiccant rotor at the optimal rotation speed was investigated. It was re-confirmed that the whole region of the direction of air flow of a rotor has not necessarily reached a regeneration temperatures. This state of regeneration balanced with the highly amount of adsorption. Purge air should be supplied to the rotor in the same direction as adsorption air. Otherwise, meaningless heat transfer arises inside a rotor and the adsorbent cooling effect of purge sector disappears. Adsorbent rotor, which shows the adsorption isotherm of S-shape, indicated a very unique temperature profiles in a regeneration zone. It can be understood that it is a phenomenon which arises when the relative humidity of regeneration air arrives at the relative humidity region where the amount of adsorption changes suddenly. Temperature distribution in a rotor could deeply reflect an adsorption / desorption behavior of water vapor onto / from the adsorbent rotor. It can be concluded measurement of the temperature distribution in a desiccant rotor is useful for visualization of the simultaneous heat and mass transfer phenomena in a desiccant rotor.
Adsorption kinetics of activated carbon and high pressure gas pair was analyzed by experiment and simulation. The rise of temperature during the adsorption process affects adsorption uptake. Therefore, the simulation model took into consideration of detailed heat and mass transfer in a cylindrical adsorption bed. The results showed that the detailed heat and mass transfer model agreed with the experimental results more accurately compared with the model where the linear driving force model was solely used without the consideration of the changes in temperature and pressure. The effect of the radial direction distribution in cylindrical adsorption bed is also discussed. Although the number of the grids in radial direction decreased in simulation,the error of approximation between the model and experimental result was not changed significantly.
The purpose of this study is to develop “supply air dew point temperature” control for a desiccant air-conditioning system in a low-humidity environments to reduce overall system energy consumption. For this form of control development, we need to know the basic characteristics of the desiccant air conditioning system. As such, we analyze the effects of the operating variables on the system’s supply air dew point temperature, using the model which we construct. This report summarizes the characteristics of each operating variable, desiccant wheel rotary speed, regeneration outside air flow rate, regeneration temperature, purge air flow rate and pre-process cooling temperature, on the system’s heating and cooling energy. For example, it is found that the desiccant wheel rotary speed and purge air flow rate doesn’t have a influence to reduce total system energy but system energy decrease with a decrease in regeneration air flow rate and regeneration temperature.
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