"ANALYSIS OF NATURAL CONVECTION DOMINATED MELTING OF A PCM WITH CONJUGATE FORCED CONVECTION VIA A WALL OF FINITE CONDUCTANCE"

1994 ◽  
Author(s):  
Marcel Lacroix ◽  
Bruno Binet
Keyword(s):  
Natural Convection ◽  
Forced Convection ◽  
Convection Dominated

NUMERICAL STUDY OF NATURAL CONVECTION DOMINATED MELTING OF A PCM WITH CONJUGATE FORCED CONVECTION

1995 ◽  
Vol 19 (4) ◽  
pp. 455-469
Author(s):  
M. Lacroix
Keyword(s):  
Thermal Conductivity ◽  
Natural Convection ◽  
Forced Convection ◽  
Numerical Study ◽  
Convection Heat Transfer ◽  
Melting Process ◽  
Reynolds Numbers ◽  
Solid Liquid Interface ◽  
Solid Liquid ◽  
Convection Dominated

This paper presents a numerical analysis of natural convection dominated melting inside a rectangular enclosure coupled with forced convection heat transfer in a transport fluid via a finite conductance heat exchanging surface. A computational methodology based on a stream function-vorticity-temperature formulation is adopted and the irregular shape of the moving solid-liquid interface is treated with body-fitted coordinates. The model is then employed to investigate the interaction between natural convection in the PCM filled cavity and forced convection in the HTF. Numerical experiments were carried out for Rayleigh numbers, Ra, between 2.08‧108 and 4.60‧109, modified Reynolds numbers, Re between 4.23 and 423.0, wall-PCM thermal diffusivity ratios, α, between 5.0 and 10.0 and dimensionless wall thickness, w, between 0.005 and 0.05. Results show that the melting process is increasingly delayed by heat conduction across a wall of decreasing thermal conductivity and/or increasing thickness. This effect is accentuated for low HTF flow rates (Re ~ 4.23). On the other hand, for a wail of given thickness and thermal conductivity, the effect of increasing the HTF flow rate on the melting process becomes imperceptible for Re ≥ 4.23.

Transient Mixed-Convection With Applications to Cooling of Biomaterials

2005 ◽  
Author(s):  
Saurabh Shrivastava ◽  
Bahgat Sammakia
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Mixed Convection ◽  
Forced Convection ◽  
Convection Flow ◽  
Coupled Wall ◽  
Steady Stage ◽  
Basic Characteristics ◽  
Convection Dominated ◽  
Solid Block

2-Dimensional transient mixed-convection in a horizontal rectangular enclosed cavity heated from a lower solid block is numerically studied. The enclosure simulates the thermal reservoir for the storage and shipment of biomaterials. The lower solid block containing the thermal biomass that has adiabatic sides and bottom wall, is coupled along the top wall with a hollow cavity of aspect ratio (H/L = 0.5), whose side and top walls are assumed to be surrounded by a phase change material and has been assigned constant temperature of 273K. Initially, the temperature of the biomaterials is raised to 283K; the upper cavity is filled with quiescent air and uniform temperature at time zero. Laminar airflow is assumed with a fan in middle of the cavity. The basic characteristics and flow structures during the transition of natural-convection-dominated flow to forced-convection-dominated flow are determined. The problem is solved for the range of mixed-convection regime and the fluid flow structure and heat transfer is found to be dependent on mixed-convection as determined by the buoyancy parameter Gr/Re2. As anticipated, the forced-convection-dominated flow is found to be more effective in cooling of the thermal biomass than the natural-convection-dominated flow. This study shows that using the assisted forced convection results in an increase in the cooling performance of the biomaterial container in the natural-convection-dominated type mixed-convection flow. Examining the area averaged Surface Nusselt number along the coupled wall with time and the rate of heat transfer from the thermal biomass during the Quasi-steady stage validates the above hypothesis.

Mixed Convection Transport From an Isolated Heat Source Module on a Horizontal Plate

1990 ◽  
Vol 112 (3) ◽  
pp. 653-661 ◽  
Author(s):  
B. H. Kang ◽  
Y. Jaluria ◽  
S. S. Tewari
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Mixed Convection ◽  
Forced Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Finite Thickness ◽  
Forced Flow ◽  
Maximum Temperature ◽  
Convection Dominated

An experimental study of the mixed convective heat transfer from an isolated source of finite thickness, located on a horizontal surface in an externally induced forced flow, has been carried out. This problem is of particular interest in the cooling of electronic components and also in the thermal transport associated with various manufacturing systems, such as ovens and furnaces. The temperature distribution in the flow as well as the surface temperature variation are studied in detail. The dependence of the heat transfer rate on the mixed convection parameter and on the thickness of the heated element or source, particularly in the vicinity of the source, is investigated. The results obtained indicate that the heat transfer rate and fluid flow characteristics vary strongly with the mixed convection variables. The transition from a natural convection dominated flow to a forced convection dominated flow is studied experimentally and the basic characteristics of the two regimes determined. This transition has a strong influence on the temperature of the surface and on the heat transfer rate. As expected, the forced convection dominated flow is seen to be significantly more effective in the cooling of a heat dissipating component than a natural convection dominated flow. The location of the maximum temperature on the module surface, which corresponds to the minimum local heat transfer coefficient, is determined and discussed in terms of the underlying physical mechanisms. The results obtained are also compared with these for an element of negligible thickness and the effect of a significant module thickness on the transport is determined. Several other important aspects of fundamental and applied interest are studied in this investigation.

scholarly journals Comparative study of different drying methods regard to the phenols and flavonoids content of dried Citrus aurantium L. leaves

2021 ◽  
Author(s):  
Geovanni Hernandez Galvez ◽  
Margarita Castillo Téllez ◽  
Jorge de Jesús Chan González ◽  
Francisca Méndez Morales ◽  
Damianys Almenares López ◽  
...  
Keyword(s):  
Natural Convection ◽  
Forced Convection ◽  
Design Methodology ◽  
Total Phenol ◽  
Drying Methods ◽  
Total Flavonoids ◽  
Citrus Aurantium ◽  
Solar Drying ◽  
Solar Dryer ◽  
Total Flavonoids Content

Objective: To determine the effects of different thermal drying technologies on the total phenol and flavonoid contents (TPC) and total flavonoids (TFC) in sour orange (Citrus aurantium L.) leaves. Design/methodology/approach: Solar drying was carried out in outdoor sunny conditions using two direct solar dryers; one with natural convection, the other with forced convection. The total phenol and flavonoid contents in gallic acid equivalents (GAE) and quercetin (Q), respectively, of ethanolic extracts of C. aurantium were assessed with spectrophotometric techniques. Results: The results demonstrated maximum phenol values for the direct natural convection solar dryer (161.4 mg EAG/g MS) and minimum values for shade drying (61.43 mg EAG/g MS). As for flavonoids, the highest values were obtained in the direct forced convection solar dryer (32.22 ± 1.6 mg EQ/g MS), while the lowest was registered in the open air sun (11.72 mg EQ/g MS). Conclusions: Direct solar dryers are technologies effective for maintaining the phenols and total flavonoids content in dried leaves of C. aurantium.  

scholarly journals A Review on the Control Parameters of Natural Convection in Different Shaped Cavities with and without Nanofluid

Processes ◽  
2020 ◽  
Vol 8 (9) ◽  
pp. 1011 ◽  
Author(s):  
Sara Rostami ◽  
Saeed Aghakhani ◽  
Ahmad Hajatzadeh Pordanjani ◽  
Masoud Afrand ◽  
Goshtasp Cheraghian ◽  
...  
Keyword(s):  
Porous Media ◽  
Natural Convection ◽  
Free Convection ◽  
Forced Convection ◽  
Opposite Effect ◽  
Fluid Velocity ◽  
Experimental Studies ◽  
Effective Parameters ◽  
Magnetic Forces ◽  
Numerical Studies

Natural convection in cavities is an interesting subject for many researchers. Especially, in recent years, the number of articles written in this regard has grown enormously. This work provides a review of recent natural convection studies. At first, experimental studies were reviewed and, then, numerical studies were examined. Then, the articles were classified based on effective parameters. In each section, numerical studies were examined the parameters added to the cavity such as magnetic forces, fin, porous media and cavity angles. Moreover, studies on non-rectangular cavities were investigated. Free convection in enclosures depends more on the fluid velocity relative to the forced convection, leading to the opposite effect of some parameters that should essentially enhance rate of heat transfer. Nanoparticle addition, magnetic fields, fins, and porous media may increase forced convection. However, they can reduce free convection due to the reduction in fluid velocity. Thus, these parameters need more precision and sometimes need the optimization of effective parameters.

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