Geometrical Effects of Cabinet Size and Aspect Ratio on Heat and Mass Transfer During Open Door Conditions

2005 ◽  
Author(s):  
W. Terrell
Keyword(s):  
Mass Transfer ◽  
Aspect Ratio ◽  
Heat And Mass Transfer ◽  
Ambient Air ◽  
Open Door ◽  
Nusselt Numbers ◽  
Aspect Ratios ◽  
Mass Fluxes ◽  
Geometrical Effects ◽  
Aluminum Plates

The goal of this paper is to examine the effects of size and aspect ratio (H/L) of open cavities on heat and mass transfer during open door conditions of refrigerator cabinets. An experimental investigation was conducted using test cavities constructed from foam board insulation and interior covered with aluminum plates acting as calorimeters. Various size cavities with heights of 15.24 cm, 30.48 cm, and 45.72 cm along with aspect ratios of 0.5, 1.0, and 2.0 were tested. Cavities were heated to an initial temperature of 50°C, 60°C, 70°C, and 80°C before being exposed to the ambient air. In addition, tests were conducted in which the cavities were cooled before being exposed to the ambient. The relative humidity was varied from 60% to 75% and initial temperatures varied from 5°C, 1°C, and −5°C. The cavity mass fluxes were measured to validate the heat/mass transfer analogy for the tests. Experimental results were also presented for Rayleigh numbers from 5.88 × 106 to 2.21 × 108 with Nusselt numbers ranging from 15.48 to 53.51. The Nusselt numbers for cavities with an aspect ratio of one and two were in good agreement with each other. The Nusselt numbers for the cavity with an aspect ratio of 0.5 were slightly lower than the other cavities at given Rayleigh values.

Influence of nozzle exit geometrical parameters on supersonic jet decay

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Prasanta Kumar Mohanta ◽  
B. T. N. Sridhar ◽  
R. K. Mishra
Keyword(s):  
Aspect Ratio ◽  
Nozzle Exit ◽  
Ambient Air ◽  
Schlieren Image ◽  
Geometrical Parameters ◽  
Image Study ◽  
Aspect Ratios ◽  
Core Length ◽  
Supersonic Core Length ◽  
The Impact

Abstract Experiments and simulations were carried on C-D nozzles with four different exit geometry aspect ratios to investigate the impact of supersonic decay characteristics. Rectangular and elliptical exit geometries were considered for the study with various aspect ratios. Numerical simulations and Schlieren image study were studied and found the agreeable logical physics of decay and spread characteristics. The supersonic core decay was found to be of different length for different exit geometry aspect ratio, though the throat to exit area ratio was kept constant to maintain the same exit Mach number. The impact of nozzle exit aspect ratio geometry was responsible to enhance the mixing of primary flow with ambient air, without requiring a secondary method to increase the mixing characteristics. The higher aspect ratio resulted in better mixing when compared to lower aspect ratio exit geometry, which led to reduction in supersonic core length. The behavior of core length reduction gives the identical signature for both under-expanded and over-expanded cases. The results revealed that higher aspect ratio of the exit geometry produced smaller supersonic core length. The aspect ratio of cross section in divergent section of the nozzle was maintained constant from throat to exit to reduce flow losses.

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.

Mathematical Modeling of a Thin Layer Solar Kiln

1990 ◽  
Vol 112 (3) ◽  
pp. 196-203 ◽  
Author(s):  
Moustafa M. Elsayed
Keyword(s):  
Mathematical Modeling ◽  
Mass Transfer ◽  
Thin Layer ◽  
Heat And Mass Transfer ◽  
Initial Conditions ◽  
Ambient Air ◽  
Glass Temperature ◽  
Humidity Ratio ◽  
Solar Kiln ◽  
Empirical Relations

Mathematical modeling of a thin layer solar kiln for drying of agricultural products is presented. Governing equations of the air temperature and air humidity ratio, material temperature and its moisture content, and the glass temperature are derived together with their initial conditions. Heat and mass transfer between the material and the air and the air and the glass cover are estimated using empirical relations for the coefficients of heat and mass transfer. The results of the calculations are analyzed to predict the effect of the following parameters on the transient performance of the kiln: (a) rate of absorbed solar energy in the kiln, (b) rate of air flow through the kiln, (c) volume of the dried material, (d) ambient temperature, and (e) humidity ratio of the ambient air.

Very Deep X-Ray Lithography for Heat and Mass Transfer Applications

2004 ◽  
Author(s):  
Kevin W. Kelly ◽  
Charles Becnell ◽  
Yohannes Desta
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Heat Exchangers ◽  
Superior Performance ◽  
Length Scale ◽  
Micro Machining ◽  
X Ray ◽  
Aspect Ratios ◽  
Starting Point ◽  
Micro Features

Heat and mass transfer devices are being fabricated by International Mezzo Technologies that utilize micro features with increasingly aggressive combinations of both feature height and feature aspect ratio. Improvements in x-ray lithography using SU-8 now make it possible to lithographically define densely packed arrays of features with heights of 3 mm and with aspect ratios of around 25. These arrays potentially serve as the starting point for increasingly aggressive LIGA-based micro machining of heat exchangers, regenerators, recuperators, etc. that have superior performance due to length scale advantage.

Evaluation of Convective Heat and Mass Transfer in Open Sun and Green House Drying

2008 ◽  
Author(s):  
S. K. Shukla
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Convective Heat ◽  
Ambient Air ◽  
Natural Mode ◽  
Transfer Coefficients ◽  
Drying Time ◽  
Sun Drying ◽  
Green House ◽  
Hourly Data

In this communication, a study on open sun and green house drying has been performed to evaluate the convective heat and mass transfer coefficients as a function of climatic parameters. The hourly data for the rate of moisture removal, crop temperature, relative humidity inside greenhouse and outside greenhouse and ambient air temperature for complete drying have been recorded. The experiments were done in the premises of Allahabad Agricultural Institute-Deemed University, after the crop-harvesting season from February 2006 to April 2006. Using these data, the value of convective heat and mass transfer in open sun drying (OSD) and green house sun drying (GHD) under natural and forced convection mode, have been calculated. Also the empirical relations of convective heat and mass transfer with drying time under natural and forced modes have been developed. On the basis of the present study, it is inferred that the value of convective heat and mass transfer is more in open sun drying than in the green house drying under natural convection mode. However its value increases in forced mode of greenhouse drying as compared to natural mode in the initial stage of drying.

Heat and Mass Transfer in Wet Fibroporous Material Considering Moisture Evaporation

2015 ◽  
Vol 1097 ◽  
pp. 51-55
Author(s):  
V.Yu. Polovnikov ◽  
E.V. Gubina
Keyword(s):  
Thermal Conductivity ◽  
Numerical Simulation ◽  
Mass Transfer ◽  
Heat Flux ◽  
Effective Thermal Conductivity ◽  
Heat And Mass Transfer ◽  
Total Heat Flux ◽  
Moisture Evaporation ◽  
Volume Fractions ◽  
Mass Fluxes

Results of numerical simulation of heat and mass transfer in a wet fibroporous material in conditions of evaporation and steam diffusion were completed. Values of heat and mass fluxes were established. The contribution of evaporation effect to total heat flux and need to consider volume fractions of water and steam into the structure of fibroporous material in calculation of effective thermal conductivity were shown. Nonstationarity of heat and mass transfer in conditions of considered problem can be ignored.

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