Heat and Mass Transfer Analysis of a Pot-in-Pot Refrigerator Using Reynolds Flow Model

2016 ◽  
Vol 8 (3) ◽  
Author(s):  
Ramendra Pandey ◽  
Bala Pesala
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Ambient Temperature ◽  
Heat And Mass Transfer ◽  
Heat Load ◽  
Radiation Heat Transfer ◽  
Ambient Air ◽  
Total Heat ◽  
Maximum Efficiency ◽  
Radiation Heat

Heat and mass transfer analysis of evaporative cooling process in a pot-in-pot cooling system is done based on Reynolds flow hypotheses. The model proposed herein assumes that the heat transfer due to natural convection is coupled with an imaginary ambient air mass flow rate (gAo) which is an essential assumption in order to arrive at the solution for the rate of water evaporation. Effect of several parameters on the pot-in-pot system performance has been studied. The equations are iteratively solved and detailed results are presented to evaluate the cooling performance with respect to various parameters: ambient temperature, relative humidity (RH), pot height, pot radius, total heat load, thermal and hydraulic conductivity, and radiation heat transfer. It was found that pot height, pot radius, total heat load, and radiation heat transfer play a critical role in the performance of the system. The model predicts that at an ambient temperature of 50 °C and RH of 40%, the system achieves a maximum efficiency of 73.44% resulting in a temperature difference of nearly 20 °C. Similarly, for a temperature of 30 °C and RH of 80%, the system efficiency was minimum at 14.79%, thereby verifying the usual concept that the pot-in-pot system is best suited for hot and dry ambient conditions.

Forced convection heat and mass transfer of MHD nanofluid flow inside a porous microchannel with chemical reaction on the walls

2015 ◽  
Vol 32 (8) ◽  
pp. 2419-2442 ◽  
Author(s):  
S. A. Moshizi
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Transfer Rate ◽  
Uniform Magnetic Field ◽  
Hartmann Number ◽  
Total Heat ◽  
Slip Parameter ◽  
Total Heat Transfer ◽  
Content Type

Purpose – The purpose of this paper is to focus on convective heat and mass transfer characteristics of Cu-water nanofluid inside a porous microchannel in the presence of a uniform magnetic field. The walls of the microchannel are subjected to constant asymmetric heat fluxes and also the first order catalytic reaction. To represent the non-equilibrium region near the surfaces, the Navier’s slip condition is considered at the surfaces because of the non-adherence of the fluid-solid interface and the microscopic roughness in microchannels. Design/methodology/approach – Employing the Brinkman model for the flow in the porous medium and the “clear fluid compatible” model as a viscous dissipation model, the conservative partial differential equations have been transformed into a system of ordinary ones via the similarity variables. Closed form exact solutions are obtained analytically based on dimensionless parameters of velocity, temperature and species concentration. Findings – Results show that the addition of Cu-nanoparticles to the fluid has a significant influence on decreasing concentration, temperature distribution at the both walls and velocity profile along the microchannel. In addition, total heat transfer in microchannel increases as nanoparticles add to the fluid. Slip parameter and Hartmann number have the decreasing effects on concentration and temperature distributions. Slip parameter leads to increase velocity profiles, while Hartmann number has an opposite trend in velocity profiles. These two parameters increase the total heat transfer rate significantly. Originality/value – In the present study, a comprehensive analytical solution has been obtained for convective heat and mass transfer characteristics of Cu-water nanofluid inside a porous microchannel in the presence of a uniform magnetic field. Finally, the effects of several parameters such as Darcy number, nanoparticle volume fraction, slip parameter, Hartmann number, Brinkman number, asymmetric heat flux parameter, Soret and Damkohler numbers on total heat transfer rate and fluid flow profiles are studied in more detail. To the best of author’s knowledge, no study has been conducted to this subject and the results are original.

THE EFFECT OF DIFFERENT AMBIENT TEMPERATURE TO SOLAR COOLING PERFORMANCE

2016 ◽  
Vol 78 (5-5) ◽  
Author(s):  
Dewanto Harjunowibowo ◽  
Dina Nur Adilah ◽  
Dwi Teguh Rahardjo ◽  
Danar S. Wijayanto ◽  
Fredy Surahmanto ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Ambient Temperature ◽  
Heat And Mass Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Adsorption Process ◽  
Mass Transfer Rate ◽  
Cooling Performance ◽  
Solar Cooling

The density of adsorbent bed significantly contributed to solar cooling performance (COP). The density determines how well the heat and mass transfer are. Besides that, the COP is also determined by ambient temperature. This research aims to investigate the affect of temperature of a connecting pipe, as a representative of different ambient temperature against a solar cooling machine performance. The experiment will show in what condition a solar cooling is going to have a better cooling result. The data used in this case was taken experimentally and conducted using a solar cooling machine equipped with temperature measurement units such as thermocouple logger. For cold ambient temperature, in adsorption process, refrigerant vapour flows to the generator through the connecting pipe cooled by water and kept steady. The results show that the COP, heat and mass transfer of adsorbent bed of the system in the adsorption process on a warm condition are better than in a cold environment. In the warm condition the COP system is 0.24, the heat transfer rate is 0.06 °C/minute, and the mass transfer rate is 1.09 ml/minute. Whereas, in the cold condition the COP system is 0.23, the heat transfer rate is 0.05 °C/minute, and the mass transfer rate is 1.04 ml/minute. 

Simultaneous Heat and Mass Transfer From a Two-Dimensional, Partially Liquid-Covered Surface

1991 ◽  
Vol 113 (4) ◽  
pp. 874-882 ◽  
Author(s):  
Y.-X. Tao ◽  
M. Kaviany
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Reynolds Number ◽  
Surface Temperature ◽  
Heat And Mass Transfer ◽  
Solid Surface ◽  
Transfer Rate ◽  
Mass Transfer Rate ◽  
Ambient Air ◽  
Simultaneous Heat

Simultaneous heat and mass transfer from partially liquid-covered surfaces is examined experimentally using a surface made of cylinders with the voids filled with liquid. The steady-state evaporation rate, surface temperature of the liquid and exposed solid, and location of meniscus are measured for various ambient air velocities and temperatures. Using these, we examine the effect of the extent to which the liquid covers the surface on the evaporation mass transfer rate resulting from the convective heat transfer from the ambient gas to this surface. The results show strong Bond and Reynolds number effects. For small Bond and Reynolds numbers, the presence of dry (exposed solid) surface does not influence the mass transfer rate. As the Bond or Reynolds number increases, a critical liquid coverage is found below which the mass transfer begins to decrease. Heat transfer from the exposed solid to the liquid is also examined using the measured surface temperature, a conduction model, and an estimate of the liquid and solid surface areas (using a static formation for the liquid meniscus). The results show that at the liquid surface an analogy between heat and mass transfer does not exist.

Variation of Heat and Mass Transfer Coefficients During Drying of Granular Beds

1990 ◽  
Vol 112 (3) ◽  
pp. 668-674 ◽  
Author(s):  
J. A. Rogers ◽  
M. Kaviany
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Evaporation Rate ◽  
Ambient Air ◽  
Spherical Particles ◽  
Convective Drying ◽  
Transfer Processes ◽  
Surface Areas ◽  
Mass Transfer Processes

During convective drying of initially fully saturated granular beds, the solid matrix is gradually exposed to the ambient air, resulting in heat transfer to both the liquid and solid. In an attempt to examine the heat and mass transfer processes occurring on the surface and to examine the influence of particle size and Bond number on the drying rate, experiments are performed in which granular beds constructed of spherical particles (which range from d = 0.2 mm to d = 25.4 mm) are convectively dried. For beds constructed of very small particles (d = 0.2 mm, Bo = 0.0035) the surface areas of the liquid and solid are difficult to estimate due to the random arrangement of the particles. The experimental results confirm existing knowledge that the evaporation rate is nearly constant during the funicular state of drying. For beds constructed of large particles (d = 25.4 mm, Bo = 21.7) an estimate of the surface areas of the liquid and solid reveals that the surface areas and the evaporation rate are highly dependent on surface saturation, contact angle, and surface tension. The results indicate that heat transfer from the solid to the liquid is significant and that the heat and mass transfer processes are not analogous.

Overall Efficiency of a Radial Fin Assembly Under Dehumidifying Conditions

1998 ◽  
Vol 120 (4) ◽  
pp. 299-304 ◽  
Author(s):  
L. Rosario ◽  
M. M. Rahman
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Exchanger ◽  
Relative Humidity ◽  
Heat And Mass Transfer ◽  
Heat Transfer Rate ◽  
Transfer Process ◽  
Transfer Rate ◽  
Total Heat ◽  
Overall Efficiency

The aim of this paper is the analysis of heat transfer in a radial fin assembly during the process of dehumidification. An individual finned tube geometry is a reasonable representation of heat exchangers used in air conditioning. The condensation process involves both heat and mass transfer and the cooling takes place by the removal of sensible as well as latent heat. The ratio of sensible to total heat is an important quantity that defines the heat transfer process during a dehumidifier operation. A one-dimensional model for heat transfer in the fin and the heat exchanger block is developed to study the effects of condensation on the fin surface. The combined heat and mass transfer process is modeled by incorporating the ratio of sensible to total heat in the formulation. The augmentation of heat transfer due to fin was established by comparing the heat transfer rate with and without fins under the same operating conditions. Calculations were carried out to study the effects of relative humidity and dry bulb temperature of the incoming air, and cold fluid temperature inside the coil on the performance of the heat exchanger. An analysis of the overall efficiency for the assembly was also done. Results were compared to those under dry conditions, wherever appropriate. Comparison between present results and those published for rectangular as well as radial fins under fully wet conditions were made. These comparisons established the validity of the present model. It was found that the heat transfer rate increased with increment in both dry bulb temperature and relative humidity of the air. The augmentation factor, however, decreased with increment in relative humidity and the dry bulb temperature. The fin efficiency decreased with relative humidity.

scholarly journals AFFECTING PARAMETERS TO THE HEAT AND MASS TRANSFER OF NH3-H2O SOLUTION FALLING ON THE HORIZONTAL ROUND TUBE

2021 ◽  
Vol 45 (03) ◽  
Author(s):  
NGUYEN HIEU NGHIA ◽  
LE CHI HIEP ◽  
DUONG CONG TRUYEN
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat And Mass Transfer ◽  
Heat Load ◽  
Tube Length ◽  
Absorption Refrigeration ◽  
Absorption Process ◽  
The Heat Transfer Coefficient

The absorption process has been confirmed as the most important process in absorption refrigeration machines in terms of improving their total efficiency. One of the key research directions is the selection of absorber structure which is expected to be fabricated in Vietnam without demand of new infrastructure investment. In this study, a local model of the coupled heat and mass transfer during absorption process of NH3 vapor by a NH3-H2O diluted solution flowing over horizontal round tubes of an absorber was made. The heat transfer coefficient obtained from the coupled heat and mass transfer mathematic model. This heat transfer coefficient is used to calculate the variation of the simulated value of heat load. The correlations which give the heat transfer coefficient and mass transfer coefficient in the absorption process in range of solution concentration ω = 28% ÷ 31%, solution mass flow rate per unit tube length Γ = 0.001 ÷ 0.03 kgm-1s-1, coolant temperature twater = 28 oC ÷ 38 oC are set as two functions. The practical decrease of wetted ratio analyses were taken into account when the solution flow from the top to the bottom of the parallel tube bundle. The deviation of theoretical heat load and experimental heat load is about 12.3%. Based on these simulations, the theoretical studies were done for absorption refrigeration system in order to narrow the working area where the experiments later focused on. The results of this study will be the basis for subsequent application research of falling film absorbers.

Sign in / Sign up

Export Citation Format

Share Document