Publications
Experimental investigation for vapor compression system performance enhancement through condenser cooling by using shallow fluidized bed
Oct 1, 2023Journal JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY
Publisher Springer Science and Business Media B.V.
DOI 10.1007/s10973-023-12495-5
Issue 21
Volume 148
A vapor compression cycle is a mechanical heat transfer device that moves heat from a lower-temperature sink to a higher-temperature sink. In vapor compression refrigeration, the condenser can remove heat from the system when it is hot and this heat can be rejected by air or water. The present work concentrates on an investigation that has been carried out experimentally of performance enhancement of a compression cycle with a shallow fluidized bed utilized to cool the condenser. The homogeneous particle size (0.5 mm) in the shallow fluidized bed helps to remove heat generated by the condenser; in order to guarantee adequate particle mixing, the surface of the bed kept approximately 2.5 cm high. The result shows that amount of coefficient of performance and power consumption of the compressor improvement ranges about 49.3 and 18.53%, respectively, by using the shallow fluidized bed for the condenser compared without condenser's shallow fluidized bed. Additionally, the condenser with a shallow fluidized bed obtained the best COP at an temperature of the evaporator of 8 & DEG;C, with an estimated value of 3.217. Moreover, when utilizing a shallow fluidized bed, the heat rejection ratio values reduced by about 35.7% when compared to the range of (H.R.R.) without a shallow fluidized bed. It is also observed that the amount of refrigerating effect values will improve when the condenser is immersed in the shallow fluidized bed ranges about 18.53% at times 60 min., compared without shallow fluidized bed for the condenser.
Conjugate local thermal nonequilibrium and non-Darcy flow inside porous enclosure: Analysis of localized heating and cooling arrangements
Jul 17, 2023Journal HEAT TRANSFER
Publisher John Wiley and Sons Inc
DOI 10.1002/htj.22923
Issue 8
Volume 52
This study covers a simulation on conjugate free convective in a porous enclosure containing a side wall thickness and partially heated and cooled from sides under the considerations of local thermal nonequilibrium (LTNE) and non-Darcy flow. Interest has been focused on how the side wall thickness and the locations of cooled and heated parts affect the effectiveness of the Nusselt number (Nu). Three different cases of localized heating and cooling locations have been implemented for the following ranges: scaled heat transfer coefficient (0.1 & LE;H & LE;100 $0.1\le H\le 100$), wall to fluid thermal conductivity ratio (0.1 & LE;Rk & LE;100 $0.1{\le R}_{k}\le 100$), modified Rayleigh number (200 & LE;Ra*& LE;1000 $200\le {Ra}* \le 1000$), wall width (0.1 & LE;Z& LE;0.5 $0.1\le \hat{Z}\le 0.5$), inertial parameter (10-4 & LE;Fs/Pr*& LE;10-2 ${10}<^>{-4}{\le F}_{s}/{P}_{r}<^>{* }\le {10}<^>{-2}$), and thermal conductivity ratio (0.1 & LE;Kr & LE;100 $0.1\le {K}_{r}\le 100$). Outcomes show that Z $\hat{Z}$ and the locations of cooled and heated parts have remarkable impacts on all the Nusselt numbers. The intensity of LTNE region considerably relies on Ra* ${Ra}{* }$, Kr ${K}_{r}$ and H $H$. The total average Nu(T) is highly dependent on Rk ${R}_{k}$, Ra* ${Ra}{* }$, Z $\hat{Z}$, Fs/Pr* ${F}_{s}/{P}_{r}<^>{* }$, and Kr ${K}_{r}$ as compared to H. The increase in Z $\hat{Z}$ leads to change of the convective mechanism to conductive mode. The rise in Rk ${R}_{k}$ guides to increase Nu, where Rk ${R}_{k}$ can control the flow strength. The actions of Fs/Pr* ${F}_{s}/{P}_{r}<^>{* }$ on Nu(f) is more evident than Nu(s). For low H and K-r, the size of LTNE zone is considerably affected by H as compared to K-r although K-r has a high influence on Nu. For high K-r and H, the LTNE zone has closely vanished. Findings display that the Case 2 provided the highest Nu for all tested parameters except the case of Kr=0.1 ${K}_{r}=0.1$. Finally, it is evident that for the problems that employed solid conduction wall with localized heating and cooling sections, Case 2 is recommended for future use in the applications that implement a porous medium and depend on free convection.
Impact of using triple adiabatic obstacles on natural convection inside porous cavity under non-darcy flow and local thermal non-equilibrium model
May 15, 2021Journal INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER
Publisher Elsevier Ltd
DOI 10.1016/j.icheatmasstransfer.2021.105760
Volume 130
This work displays a numerical investigation on free convection inside non-Darcy porous cavity having a vertical triple adiabatic obstacles under conditions of Local thermal non-equilibrium (LTNE). Interesting has been focused on how the obstacles lengths arrangements manipulates the enhancement of free convection. Based on obstacles lengths, seven cases have been tested under large ranges of heat transfer coefficient (0.1 <= H <= 100), ratio of thermal conductivity (0.1 <= K-r <= 100), obstacles length (0.25 L <= Z <= 0.75 L), modified Rayleigh number (200 <= Ra* <= 1000) and inertia coefficient (10(-4) <= Fs/Pr* <= 10(-2)). Results indicate that the optimum improvement in Nu can be obtained when using small length of all obstacles or the obstacle length should be set in ascending order. The presence of obstacles reduces the heat transfer as compared to its absence. Therefore, the case that has a minimum obstacles length is advised to be used for applications of porous heat exchangers that involved adiabatic obstacles. A significant improvement in Nu is obtained with rising in Ra*, H and K-r and reducing in Fs/Pr*. The density of LTNE region is extremely reduced with rising in H, K-r and Ra* and reducing in Z and Fs/Pr*. The thermal equilibrium case can be reached when using large values of H and K-r.
Effect of suction or blowing on velocity and temperature distribution of flow over a flat plate
May 13, 2021Journal MATERIALS TODAY-PROCEEDINGS
Publisher Elsevier Ltd
DOI 10.1016/j.matpr.2020.12.735
Volume 42
In this paper, laminar, incompressible flow with constant pressure gradient and constant wall temperature over a flat plate for several values of fluid suction and blowing parameters at beta = -0.1978, m = -0.09 and beta = 0.66, m = 0.5 respectively were studied numerically. The governing nonlinear partial differential equations are transformed to ordinary differential equations by using a similarity variable and then solved numerically adopting Runge-Kutta integration method. Effects of continuous suction and blowing with very low ratio of constant velocity to free stream neglecting the mass transfer on the velocity, temperature profiles and skin friction are presented. The results indicated that the skin friction factor is increased with increase the value of the suction for given Reynolds number. In order to reduce the skin friction, the laminar flow and avoid transition the blowing have been applied. The effect of fluid blowing parameter on velocity profile in hydrodynamic boundary layer are the certain incidence angles. Results show that the hydrodynamic boundary layer thickness is increased due to the blowing. It can be noted that the delaying separation is led to increase of the maximum lift. It was observed that increasing the maximum lift by maintain laminar flow to avoid transition and delaying separation to reduce skin friction is existing by suitable magnitude of suction or blowing. It is concluded that the skin friction is decreasing due to apply the blowing over a flat plate. (C) 2021 Elsevier Ltd. All rights reserved.
Natural convection heat transfer from a bank of orthogonal heated plates embedded in a porous medium using LTNE model: A comparison between in-line and staggered arrangements
Dec 31, 2020Journal INTERNATIONAL JOURNAL OF THERMAL SCIENCES
Publisher Elsevier Masson s.r.l.
DOI 10.1016/j.ijthermalsci.2020.106692
Volume 160
This study numerically presents the characteristics of natural convection induced by a bank of orthogonal heated plates instilled inside porous cavity using the assumption of local thermal non-equilibrium (LTNE) and nonDarcian conditions. In-line and staggered arrangements of heated sections have been investigated for the purpose of comparison. Attention has been given on how the arrangement of heated sections affects the performance of heat transfer for various related parameters. Numerical solutions demonstrated that the average Nusselt number (Nu) is robustly depends on thermal conductivity ratio (K-r), inertia parameter (Fs/Pr*) and modified Rayleigh number (Ra*) in comparison with scaled heat transfer coefficient (H). The results show that the solid Nusselt number (Nu(s)) is lower than fluid Nusselt number (Nu(f)) for same value of Fs/Pr* owing to Fs/Pr* is directly affected on the fluid phase. Although K-r has a considerable effect on all Nu in comparison with H, H has a substantial impact on the strength of LTNE zone as compared to K-r, particularly for smaller K-r and H. The medium inside the enclosure nearly reaches the equilibrium condition for larger values of H and K-r. Most importantly, the results indicated that the performance of in-line arrangement is better than that obtained with staggered ones. Therefore, in-line arrangement can be recommended to be employed in manufacturing flat heat exchangers for applications involving porous media under natural convection case.
Analysis of effects of Thermal Non-Equilibrium and Non-Darcy Flow on Natural Convection in a Square Porous Enclosure Provided with a Heated L Shape Plate
Aug 7, 2010Journal INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES
Publisher Elsevier Ltd
DOI 10.1016/j.ijmecsci.2020.105704
Volume 181
This work involves a study on the convective heat transfer over a two perpendicular plates embedded inside a square porous cavity using non-Darcian flow and Local Thermal Non-Equilibrium (LTNE) assumptions. The problem has been assumed to be steady and two-dimensional coordinates. For non-Darcy flow, the effects of inertia and boundary layer have been included. Finite volume method has been used to discretize and solve the governing equations. The results show that the total average Nusselt number (Nu(T)) is a strong function of modified Rayleigh number (Ra*) and inertia parameter (Fs/Pr*). For a fixed Fs/Pr* , the fluid Nusselt number (Nu(f)) has been found higher than the solid Nusselt number (MO. The results also demonstrated that the thermal conductivity ratio (K-r) has a significant impact on all average Nusselt numbers compared to the scaled heat transfer coefficient (H). However, H has a considerable influence on the intensity of LTNE region in comparison to K-r, especially for their lower values. The size and the power of LTNE region are increased with increasing in Ra* and decreasing in Fs/Pr* . For higher K-r and H, the medium inside cavity be close to the thermal equilibrium condition. The results show that the effect of K-r on all Nu is comprehensive, whereas the effect of H is limited to Nu(s) and hence, the behaviour of Nu(T) is similar to the behaviour of Nu(f). As K-r is increased, Nu(T) becomes very close to Nu(f). Finally, the obtained results have been summarised by developing a correlation of Nu(T )which can be used in engineering design.