Enclosures natural cooling

Vk, Vk2 and Vk (W. when considering the outdoor part) can thus be determined. The total heal, Vk, so generated can be naturally dissipated through the enclosure by radiation and convection. If natural cooling is not adequate, forced cooling can be adopted through forced air or water. But precautions must be taken to ensure that the system is protected from absorbing dirt, dust or moisture from the atmosphere. 

Because of their nature, cooling towers aren t incorporated into the overall enclosures that are packaged commercial vapor degreasers. These are large, emit thousands of cubic feet of wet air per minute, and older models can make significant noise. See Figure 1.30 which is courtesy of http /A ww.ditrade.com. 

By forced convection The factors that can influence the temperature of the enclosure, installed outdoors are wind and snow, other than forced cooling. But their effect on actual cooling may be small. Sometimes this happens and sometimes not. It is better to ignore this effect when estimating various thermal effects. Natural convection and radiation will take account of this. 

Free convection in inclined enclosures is discussed by Dropkin and Somerscales [12], Evans and Stefany [9] have shown that transient natural-convection heating or cooling in closed vertical or horizontal cylindrical enclosures may be calculated with... 

The characteristics of heat transfer through a horizontal enclosure depend ou whether the hotter plate is at the top or at the bottom, as shown in Fig. 9-22. When the hotter plate is at the top, no convection currents develop in the enclosure, since Ihe lighter fluid is always on top of the heavier fluid. Heat transfer in tlris case is by pure conduction, and we have Nu - 1. When the hotter plate is at the bottom, the heavier fluid will be on top of the lighter fluid, and there will be a tendency for Ihe lighter fluid to topple the heavier fluid and rise to the top, where it comes in contact with the cooler plate and cools down. Until that happens, however, heat transfer is still by pure couduc-tion and Nu — I. When Ra > 1708, the buoyant force overcomes the fluid resistance and initiates natural convection currents, which are observed to be in the form of hexagonal cells called BSnard cells. For Ra > 3 X 10, the cells break down and the fluid motion becomes turbulent. 

The first section presents some fundamental ideas that are frequently referred to in the remainder of the chapter. The next three sections deal with the major topics in natural convection. The first of these addresses problems of heat exchange between a body and an extensive quiescent ambient fluid, such as that depicted in Fig. 4.1a. Open cavity problems, such as natural convection in fin arrays or through cooling slots (Fig. 4.1fe), are considered next. The last major section deals with natural convection in enclosures, such as in the annulus between cylinders (Fig. 4.1c). The remaining sections present results for special topics including transient convection, natural convection with internal heat generation, mixed convection, and natural convection in porous media. 

Hideo, I. Yanlai, Z. Akihiko, H. Naoto, H. Numerical simulation of natural convection of latent heat phase-change-material microcapsulate slurry packed in a horizontal rectangular enclosure heated from below and cooled from above. Heat Mass Transfer 43 (2007) 459-470. 

Due of the uncertain nature of an incident and the potential responses of the emergency services, it is difficult to calculate the capacity of containment areas, including bunded enclosures in a way that makes a realistic allowance for fire fighting media that may be used to deal with an incident. However, since many incidents are likely to involve fire, and almost all worst case scenarios involve fire, making adequate provision for retention of fire fighting and cooling water is of critical importance. 

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