Abstract: The invention includes a heat transfer geometry having first and second flow channels in parallel with each other. The flow cross-sectional area of individual channels varies along the length of the flowpath, with one channel undergoing an expansion and the other undergoing a contraction. Different amounts of additional heat transfer surface are located within different regions. In at least some instances, contraction and expansion may occur as a result of a shift of both the left and right boundaries which principally define the channel, and may occur symmetrically with respect to a centerline of the individual channel. With a cell being a first channel and associated second channel, the overall exiting flow may be offset slightly from the overall entering flow. An array may be formed containing multiple cells, and cells at edges of the array may be atypical so that the overall array fits within a simple geometric envelope.

Abstract: An arrangement of fins or other convective heat transfer surfaces which provides an improved value of heat transfer per unit pressure drop of the flowing fluid, for a defined geometric envelope. There are at least two flowpaths in parallel. Each flowpath contains a wide densely-surfaced region, called a heat transfer region, which accomplishes heat transfer at a reduced velocity whereby the ratio of heat transfer to pressure drop for that region is improved. In series with that region, in the same flowpath, is a narrow sparsely-surfaced region, called a fluid flow region, which serves to transport the fluid, at higher velocity but with minimal pressure drop, through the region(s) not densely-surfaced. The respective wide and narrow regions can be oppositely placed so that the overall arrangement maintains a constant width dimension so as to resemble conventional design.

Abstract: A flowmeter based on the pressure difference across a flow resistance element which is an array of surfaces generally parallel to the flow direction, which is operated such that over at least part of its range the Reynolds number is larger than the traditional limiting Reynolds number for laminar flow of approximately 2000. Also, the L/D ratio is shorter than in a traditional laminar flow element, so that for at least part of its range its operation is determined by the behavior of boundary layers forming on those surfaces. Such a flow resistance element provides a pressure drop vs. flowrate relationship which over a wide range of flow conditions is less steep than quadratic. This allows a larger flowrate turndown ratio for a given range of differential pressure measurement. The flowmeter may additionally comprise other sensors and a microprocessor.

Abstract: A source of thermal radiation for calibrating or testing infrared thermometers or detectors, in which improved temperature uniformity of the radiation-emitting surface is achieved by supplying heat to that surface by condensation of a working fluid as in a heat pipe. With appropriate selection of the working fluid, a wide range of temperatures is possible. Air convection currents at the radiation-emitting opening of the device may be suppressed by creation of a transition region of heated air by a baffle and air heater, further improving the temperature uniformity of the radiation-emitting surface.

Abstract: A temperature-controlled chamber, such as an inerted oven for soldering, in which the buoyancy-induced motion of gas at the opening of the chamber is suppressed by adjusting the densities of gases. In one embodiment the inertant gas is chosen to be a mixture of inert gases such that the density of warm gas inside the oven approximately equals the density of the external atmosphere. In another embodiment, a buffer region of density-matched warm air is provided between the warm inertant inside the oven and the external atmosphere. The result is reduction in the consumption of inertant.