Fluid handling – Processes
Reexamination Certificate
1998-06-05
2001-11-06
Chambers, A. Michael (Department: 3753)
Fluid handling
Processes
C137S338000, C137S375000, C165S047000, C165S135000, C138S105000, C138S148000, C251S368000
Reexamination Certificate
active
06311710
ABSTRACT:
BACKGROUND OF THE INVENTION
Heat transfer between a body and its surrounding environment is an inherent response to a non-uniform temperature distribution between the body and the environment. Limiting heat transfer between a body and its environment is highly desirable in many situations. Such heat transfer is the result of conduction, convection, and radiation. Heat transfer by convection occurs when natural forces such as gravity and buoyancy (either positive or negative) due to a temperature gradient between a body and its fluidous environment, and possibly external forces such as a fan, cause the fluidous environment to flow about the body and transfer heat to or from that body. Heretofore, conductive heat transfer was the primary means of control and it was sought by placing one or more layers of an insulating material around the body. Insulation, however, is often expensive, not intended nor effective at dealing with controlling convective heat transfer, difficult to install, and can deteriorate over time. Moreover, some insulation materials, e.g. asbestos, have proven harmful to the environment and man.
Jaber et al., Optimal Location of a District-Heating Pipeline Within a Rectangular Duct, Applied Energy, 40, pp. 101-109 (1991), considered the problem of heat transfer in natural convection flow over an insulated horizontal hot-water pipe embedded within an air filled, relatively cold, rectangular air-filled duct. The data suggest an optimal configuration in terms of pipe location relative to the cavity walls which could result in a minimum rate of heat loss from the pipe. Similarly, Jaber et al, Optimal Thermal-Insulation Placement of District-Heating Pipes and Their Support Baffles in Air Filled Trenches, Applied Energy, 40, pp. 111-118 (1991), investigated the steady state heat-transfer across a cold, horizontal, rectangular cavity enclosing two relatively hot horizontal pipes. The data suggest that the minimum steady-state heat loss occurs when the two pipes were placed one above the other. The analysis suggests that effective thermal resistance can further be enhanced by physically supporting each pipe with a pair of low conductivity physical support structures which are termed baffles. The support structures form isolated air spaces in a closed environment. Jaber et al only deal with heated pipes located within cold ducts.
Neale et al, Steady State Heat Transfers Across an Obstructed Air-Filled Rectangular Cavity, Chem. Eng. Res. Des., 66, pp. 458-462 (1988) considered the problem of heat transfer from a hot horizontal pipe embedded inside a cold, horizontal, rectangular, air-filled duct. The pipe was assumed to be supported by two, low-conductivity, symmetrically-placed spacers that completely bridge the gap between the pipe and the walls of the duct and extend the length of the pipe. The article suggests that the presence of such spacers could improve the thermal resistance of the air-filled cavity over an unobstructed one. The article is limited to pipes located in a closed environment, i.e. an air-filled duct.
Lai, Improving Effectiveness of Pipe Insulation By Using Radial Baffles to Suppress Natural Convection, Int. J. Mass Heat Transfer, 36, pp. 899-906 (1993) discloses the use of baffles solely as an integral part of porous media insulation, i.e. located within the insulation. There is no suggestion of extending the baffles beyond the insulation to further reduce heat loss from the pipe.
Accordingly, there remains a need for improved control or reduction of heat transfer between a body and its fluidous environment without the need of bulky, expensive layers of insulating materials. There is a need to minimize heat transfer between a body, e.g. a pipe, and its environment without going to the extreme of placing the body in an air-filled cavity or isolated duct or for relocating the body.
SUMMARY OF THE INVENTION
The present invention is directed to products and methods for reducing heat transfer between a body and its surrounding fluidous environment which are at different temperatures. This is done by placing at least one baffle-insulator adjacent a body in its fluidous environment. The baffle-insulator has a thermal conductivity of less than about 5 watts/meter-° K., extends into the fluidous environment modifies/weakens the flow of that fluidous environment around the body sufficiently to cause a reduction in convective heat transfer between the body and the fluidous environment.
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Brown Harry L.
Facas Georges
Chambers A. Michael
Lahive & Cockfield LLP
Powermass Corporation
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