A numerical investigation of double effect adsorption refrigeration cycle using Silica-gel/FAM-Z01 pair as adsorbent is studied in this paper. The proposed cycle is based on the cascading adsorption cycle, where condensation heat produced in the top cycle is utilized as driving heat source for the bottom cycle. Results show that this cycle produces higher COP and SCP compared to Silica-gel/Silica-gel double effect cycle for driving temperature observed between 90ºC and 150ºC, when cycle averaged chilled water temperature is fixed at 10ºC. Moreover, between 130ºC and 150ºC, COP take the maximum value when cycle time range from 1100s until 1300s. It is also observed that adsorbent mass ratio of high temperature cycle (HTC) to low temperature cycle (LTC) affects the double effect performance adsorption refrigeration cycle.
Measurements of the vapor pressure and saturated liquid density for R 245fa (1,1,1,3,3-Pentafluoropropane) were carried out using dual constant volume cells. The apparatus has two cells whose volumes are about 27 cm3 called main cell and 3 cm3 called sub cell which are immersed in a thermostat. The valve is equipped between these cells and pressure sensor is installed in a main cell to measure vapor pressure. The sample filled in the both cell, and then sub cell was fulfilled by the sample at saturation condition. The sample in the sub cell was recovered to the recovery cell using liquid nitrogen and its mass was measured. Saturated liquid density was obtained from the mass of recovered sample and inner volume of the sub cell. The vapor pressure and saturated liquid density for R 245fa were obtained in the range of temperatures from 310 to 400 K, pressures from 224 to 2203 kPa, and densities from 957 to 1306 kg‧m-3. The experimental uncertainties are estimated to be ±0.028 K in temperature, ±0.4 kPa in pressure, ±0.7 kg‧m-3 in density. On the basis of the present data, correlations of vapor pressure and saturated liquid density as a function of temperature were formulated. The experimental results were compared with the existing data.
Frost formation on the heat exchangers of low-temperature devices leads to a deterioration of the COP of the devices because frost acts as a thermally resistive layer. In the recent times, various energy-saving technologies are being sought, and advances in the technologies to reduce the frost formation are much needed. In order to reduce the frosting, it can be stated that the two quantities, the frost layer thickness and amount of frost, need to be reduced. However, an innovative method to do so has not surfaced so far. In the present work, with the aim of controlling the frost crystal formation and growth, micro-machining was done to form stripe shapes on the cooling surface, and the effects of their geometries on the frost formation were investigated. Further, the force required to scrape the frost from the cooling surface was measured, and the effect of the machined patterns/geometries on this force was also investigated. Results reveal that both the mass transfer due to the frost formation and the scrape-off force can be reduced by micro-machining the cooling surface. Thus, the possibility of controlling the frost formation and growth by micro-machining has been demonstrated.
In this study, the pressure drop and heat transfer characteristics of single-phase flow in a smooth tube, a helical-grooved tube, and nine corrugated tubes with an outer diameter of 12.7 mm were experimentally investigated employing water as test fluid. Geometrical parameters considered for the corrugated tubes were corrugation depth (0.3, 0.5, and 0.9 mm) and corrugation pitch (4, 6, 8, 12, 15, and 20 mm). Experiments were carried out by maintaining the inlet water temperature at 20 °C and varying the flow rate from 0.005 to 0.18 kg/s. The effects of the difference in the corrugation pitch and depth on the pressure drop and heat transfer characteristics of single-phase flow in the corrugated tubes were reported. Furthermore, the measured Nusselt numbers of each tested tube were compared under the same conditions of pumping power.
In the present study, experiments were performed to observe vapor-liquid two-phase flow of a refrigerant R 410A in a horizontal small triangular channel with a glass tube and a high speed camera. The hydraulic diameter of glass tube was 0.82 mm. Based on the observation, flow patterns were classified into several flow regimes, and the effect of channel arrangement against gravity direction on the flow pattern was clarified. Furthermore, the effects of cross-sectional shape and flow direction were made clear by comparing with data of upward and downward flow in a triangular channel and horizontal flow in circular and rectangular channels previously obtained.