Patent GB-700166-A (GB)
Title: Improvements relating to methods and apparatus for use in the investigation of heat conduction and analogous problems
Inventor: COYLE MICHAEL BARNARD
IPC: G01N25/18
Filed: 1950-01-20
Abstract: 700,166. Calculating apparatus ; pressure gauges ; testing physical qualities of materials. METROPOLITAN-VICKERS ELECTRICAL CO., Ltd. Feb, 13, 1951 [Jan. 20, 1950], No. 1620/50. Classes 106 (1) and 106 (2). [Also in Group XV] In a method and apparatus for the experimental investigation of unsteady-state heat conduction problems, air or other gas represents heat with pressure representing temperature, one or more reservoirs are used whose volume represents thermal capacity, the mass flow of gas mto or out of a reservoir being proportional to pressure change, and the rate of gas flow is controlled by one or more capillary tubes or narrow ducts in accordance with the rate of heat flow in the corresponding heat path, the gas being adapted to flow in a streamline manner through the tube(s) or duct(s) so that the mass flow in the or each tube or duct is proportional to the pressure difference between the ends thereof. In the Specification, the conditions for correspondence between the apparatus and the heat flow system to be investigated are considered for cases where there is firstly a linear, and secondly a more general, relation between thermal conductivity and temperature. The invention may also be applied to analogous problems e.g. those relating to the flow of fluids through porous media. Fig. 1. shows an arrangement e.g. for simulating the radial heat flow from a lagged steam pipe. The pressure at A due to a pressure source 5, indicated by a manometer P1, represents the temperature of the outer surface of the pipe, and the closed reservoirs C1-5 connected to the midpoints of capillary tubes T1-5 represent concentric zones of lagging; the temperatures at the zone junctions are thus represented by the pressures indicated by manometers P2-5. The pressure indicated by P6 represents the outer boundary temperature, and the heat loss to atmosphere is represented by capillary tube T6. A further capillary tube T7 may be added to represent the surface heat transfer resistance between the pipe and lagging. In the arrangement of Fig. 2, which may be used to represent the heat flow through a stab of finite thickness divided into six zones, each reservoir C1-6 forms one limb of a U-tube, the other limb of which is formed by a common tank 5 filled with liquid, e.g. electrical transformer oil, the level of which is kept constant by a stand pipe 6 and pump 8. The reservoirs may be formed by apertures in a metal plate 1 which are covered by transparent bevelled plates 2, 3, Fig. 3, secured by clamping plates 40, 41 which engage gaskets 42, 43. Passages D1-6 and 44 are formed in the plate 1 for connecting the reservoirs to capillary tubes T1-7 and a manifold 4 respectively, Fig. 2. To facilitate filling and emptying of the reservoirs, the passages D1-6 may be vented to atmosphere through valves such as 46, Fig. 3, normally screwed down to close a passage 45 by a knob 52. Each capillary tube 56, Fig. 4, may be enclosed in a tube 58 mounted on a metal junction piece 53 having parts 54, 55 connected with opposite ends of the tube. The tube is carried by a removable washer 60 secured by a cap 61 and nut 62. To simulate variable values of the thermal conductivity and specific heat specially shaped cores 11, e.g. of plaster, may be inserted in the reservoirs such as C6, Fig. 2. Alternatively an open cylindrical reservoir immersed in a tank may be filled with specially shaped rings, Fig. 5 (not shown). Fig. 6 shows part of an arrangement for solving twodimensional heat-flow problems, comprising sections connected by rubber tubing R, R', and each consisting of a reservoir C, two capillary tubes T or T1 and a triple valve V. The sections may be arranged radially around a circular panel, Figs 7 and 8 (not shown), and the valves V may be parts of a multiple valve comprising relatively rotatable discs whereby all the tubes T may be sealed off from one another and from the reservoirs to facilitate the taking of readings, the reservoirs being connected to a common tank as in the arrangement of Fig. 2. The invention may be used for demonstration and instructional purposes.