Patent GB-780435-A (GB)
Title: Improvements in air or gas heaters with heat storage means
IPC: F24H7/04
Filed: 1954-10-22
Abstract: 780,435. Heating gas electrically. CONTROLLED HEAT & AIR, Ltd., and MACMILLAN, R. D. Oct. 20, 1955 [Oct. 22, 1954], No. 30564/54. Class 39(3) [Also in Groups XIII and XXXV] An air or gas heater in which a heat storage matrix heated comparatively slowly gives up its heat quickly to the air or gas for short periods at long intervals, comprises one or more units 10, 12, 14 each having a cylindrical casing 16 containing a matrix 22 which is heated by metal electric resistance bars 641, 721 and has between the inlet 181 and outlet 201 at the ends of its casing a central duct 24 containing a shutter 34 automatically adjusted by means controlled by a temperature-responsive element 901 or 921 in the outlet 201 of the unit or the outlet 52 of the heater. In the form shown, two thermocouples 901, 921, one of high and the other of low sensitivity, are provided for each unit. Each matrix comprises two sets of closely spaced, parallel, thin, flat, steel or ceramic annuli with spacing ribs. The holes at the centres of the annuli form the duct 24. The two sets of annuli are separated by a partition 30 with a central opening containing the shutter 34. The air flows either straight through the duct 24 when the shutter is open, or from the first part of the duct 24 between the annuli in one set to the annular space 26, around the partition 30 and back between the annuli in the second set to the duct 24. The shutter 34 comprises louvres connected to a piston moving in a cylinder 381, by a bellcrank lever and a rod which is cranked at the middle of the duct 24 so that the louvres below pivot in the opposite direction to those above. The piston and cylinder are parts of a servomotor system regulated by the thermocouples 901, 921 and associated amplifiers and solenoids (see Group XXXV). The matrix is heated by gas-fired radiating elements or, as shown, by two sets of electric resistances 641, 721 one set mounted in the duct 24 and the other in the annular space 26. Each set comprises two rings of metal resistance rods carried by a framework composed of electrically insulating rings and longitudinal bars. Each rod in one ring is electrically connected at one end to the adjacent rod in the other ring to form a resistance unit. The units of the set in the annular space 26 are electrically connected, as shown in Fig. 5, in four independent groups each subdivided into three banks. Each of these three banks is connected at one end to a different phase L1, L2, L3 of a three-phase A.C. supply and at the other end to a common internal annular bus-bar 1101 ... 1104. The heating rods in the inner set in the duct 24 are similarly connected in a fifth group also subdivided into three banks. The current supply to the groups of resistance units is controlled by associated thermocouples which actuate an electric control system operating ganged three-pole switches (see Group XXXV), so as to keep the resistance units within a given temperature range. Lagging is provided between the casings 16 and the outer casing 48. The casings 16 may be perforated and the casing 48 air-tight, so that if the air being heated is under pressure the shell 48 withstands the pressure.