Prakhar shukla

Bio: Prakhar shukla is an academic researcher. The author has contributed to research in topics: Heat flux & Particle image velocimetry. The author has an hindex of 2, co-authored 2 publications receiving 14 citations.

An experimental study of the Effect of capillary tube diameter and configuration on the performance of a simple vapour compression refrigeration system

Abstract: The study of the expansion device in the simple vapour compression refrigeration system is necessary in order to understand the parameters which can enhance the overall performance of the system. The experimental study was done on the capillary tubes of 31 gauge, 36 gauge and 40 gauge and each test section was studied with three distinct configurations i.e. helical coiled, straight coiled and serpentine coiled configuration. The effect of the configuration and the capillary tube diameter on the overall performance of the system was studied. The findings of the experimental study revealed that the mass flow rate is maximum for the straight configuration and is least for the helical coiled configuration. The refrigeration effect was found to be maximum for the helical coiled configuration and was found to be least for straight coiled configuration. The compressor work was found to reduce as the load was increased on the system. Decreasing the capillary tube diameter increased the mass flow rate in the system and decreased the refrigeration effect produced.

Effect of capillary tube on the performance of a simple vapour compression refrigeration system

Abstract: It is essential to study the effect of capillary tube geometry on the performance of refrigeration systems. The literature review focuses on the effect that geometrical parameters like capillary tube length, bore diameter, coil pitch, number of twist and twisted angle have on the pressure drop, coefficient of performance (COP) and mass flow rate of the system. These parameters can be further studied using physical models and mathematical modeling concepts. The parameters stated above can be further optimized in order to enhance the performance of the refrigeration system.

Investigation of onset of velocity transition in free convection over an inclined flat plate by PIV

Abstract: In this work, the experimental investigation of onset of velocity transition in free convection boundary layer over a 45° inclined plate has been carried out. Experiments were performed on a 150 mm long flat plate with uniform heat flux ranging from 100 W/m2 to 5000 W/m2. Particle image velocimetry (PIV) technique was used to determine the flow characteristics over an inclined plate. The impact of various hydrodynamic parameters such as shear stress and velocity boundary layer thickness for defining or identifying the onset of velocity transition has been discussed. Also, the influence of various values of the heat fluxes on the onset of transition has been examined. It has been observed that the initiation of transition is first manifested as an increase in the overall velocity boundary layer thickness. Therefore, the thickness of the velocity boundary layer has been used as a hydrodynamic measure to determine the streamwise distance from the leading edge where the transition begins. This distance decreases with an increase of heat flux. The critical Rayleigh number for the onset of the transition under various heating conditions has been reported. For example, the critical Rayleigh numbers for the beginning of transition at heat fluxes of 100 W/m2 and 5000 W/m2 are 6.07 × 108 and 2.73 × 109 respectively.

Investigation of free convection flow around near horizontal surfaces using particle image velocimetry

Abstract: In this work, an analysis of free convection fluid flow characteristics around a flat heated surface, slightly inclined to the horizontal, has been carried out with the help of particle image velocimetry technique. Experiments were performed on a plate immersed in water and subjected to a uniform heat flux. The influence of different inclinations of the plate and heat fluxes on the flow characteristics has been analyzed. Based on the flow characteristics, different regimes—attached, transition, and buoyant plume regime—have been identified. It is observed that the onset of transition increases with the inclination angle and decreases with the heat flux. On the other hand, the length of the transition regime increases with an increase in the inclination angle and heat flux. The plume width or plume regime is found to first decrease due to necking and then increase in the vertical direction due to horizontal diffusion. Also, an increase in heat flux and inclination angle causes an increase in plume width at a particular height from the plate. It is observed that the inner velocity boundary layer thickness decreases in the laminar regime and increases in the transition regime along the length of the plate.

A review on the two-phase pressure drop characteristics in helically coiled tubes

Abstract: Due to their compact design, ease of manufacture and enhanced heat transfer and fluid mixing properties, helically coiled tubes are widely used in a variety of industries and applications. In fact, helical tubes are the most popular from the family of coiled tube heat exchangers. This review summarises and critically reviews the studies reported in the pertinent literature on the pressure drop characteristics of two-phase flow in helically coiled tubes. The main findings and correlations for the frictional two-phase pressure drops due to: steam-water flow boiling, R-134a evaporation and condensation, air–water two-phase flow and nanofluid flows are reviewed. Therefore, the purpose of this study is to provide researchers in academia and industry with a practical summary of the relevant correlations and supporting theory for the calculation of the two-phase pressure drop in helically coiled tubes. A significant scope for further research was also identified in the fields of: air–water bubbly flow and nanofluid two phase and three-phase flows in helically coiled tubes.

An experimental study of the Effect of capillary tube diameter and configuration on the performance of a simple vapour compression refrigeration system

Abstract: The study of the expansion device in the simple vapour compression refrigeration system is necessary in order to understand the parameters which can enhance the overall performance of the system. The experimental study was done on the capillary tubes of 31 gauge, 36 gauge and 40 gauge and each test section was studied with three distinct configurations i.e. helical coiled, straight coiled and serpentine coiled configuration. The effect of the configuration and the capillary tube diameter on the overall performance of the system was studied. The findings of the experimental study revealed that the mass flow rate is maximum for the straight configuration and is least for the helical coiled configuration. The refrigeration effect was found to be maximum for the helical coiled configuration and was found to be least for straight coiled configuration. The compressor work was found to reduce as the load was increased on the system. Decreasing the capillary tube diameter increased the mass flow rate in the system and decreased the refrigeration effect produced.

Effect of Capillary Tube Length and Refrigerant Charge on the Performance of Domestic Refrigerator with R12 and R600a

Abstract: In this work, the thermodynamic performance of a domestic refrigerator was experimentally studied by simultaneously varying the refrigerant charge (mr) and the capillary tube length (L). The potential of replacing R12 by R600a was also investigated. The test rig for the experiment was a vapor compression refrigerator designed to work with R12. The enthalpy of the refrigerants R600a and R12 for each data set for the experimental conditions were obtained by using REFPROP software (version 9.0). The results show that the design temperature of -120C (according to ISO - 8187 standard) and pull – down time of 135 minutes are achieved by using 60g of R600a with L= 1.2m and 1.5m. For R12, the design temperature is achieved at pull – down time of 165 minutes with mr = 40g and L = 0.9m. The appropriate combination of L and mr for R600a to be used as a drop-in refrigerant for R12 is found to be 1.5m and 60g on the basis of power consumption per day, pull-down time and COP, whereas by considering the cooling capacity, it is 0.9 m and 60g. The cooling capacity of R600a was about 9.18% higher than that of R12, the power consumed by R600a was about 24 % lower than that of R12 and the COP of R600a was about 6.3% higher than that of R12. In conclusion, the proposed R600a seems to be an appropriate long-term candidate to replace R-12 in the existing refrigerator in terms of power consumption, cooling capacity and COP.

A comparative study on the performance of the domestic refrigerator using r600a and lpg with varying refrigerant charge and capillary tube length

Abstract: A comparative experimental study on the performance of a domestic refrigerator using R600A and LPG with a varying refrigerant charge (wr) and capillary tube length (L) was carried out. The enthalpy of the refrigerants R600A and LPG for each data set for the experimental conditions were obtained by using REFPROP soft ware (version 9.0). The results show that the design temperature and pull-down time set by ISO for a small refrigerator are achieved earlier using refrigerant charge 60 g of LPG with a 1.5 m capillary tube length. The highest COP (4.8) was obtained using 60-g charge of LPG with L of 1.5-m. The average COP obtained using LPG was 1.14% higher than that of R600A. Based on the result of electric power consumption, R600A off ered lowest power consumption. The compressor consumed 20% less power compared to LPG in the system. The system performed best with LPG in terms of COP and cooling capacity, while in terms of power consumption R600A performed best.

Experimental Evaluation of Window-Type Air-Conditioning Unit with New Expansion Device and R404A Alternative Refrigerant

Abstract: In this study, the performance of a window-type air-conditioning unit with an alternative, ozone-friendly refrigerant was enhanced by incorporating a nozzle instead of a capillary tube as an expans...