Abstract: Methods and apparatus for defrosting the outdoor coil in a variable speed heat pump system including determining, after the end of the last preceding defrosting, the optimal time to begin the next defrosting, and then initiating the defrosting responsive to the time interval since the end of the last defrosting tsD, the averages, over time, of liquid line temperature LLT, speed ES of the engine that drives the compressor, and outdoor dry bulb temperature ODT. The defrosting includes switching the system to the defrost mode at a predetermined maximum engine speed, periodically measuring the time taken during the defrosting ttD and the liquid line temperature LLT; periodically computing the rate of change of LLT with respect to time .DELTA.LLT/.DELTA.t, and when .DELTA.LLT/.DELTA.t is greater than the previous maximum value and ttD is greater than a predetermined time, storing the value of each in place of its preceding value.

Abstract: A gas engine driven heat pump system including an apparatus and method for exhaust gas dispersion and condensate removal which disperses and mixes exhaust gases more effectively to prevent local icing, inhibit frosting of outdoor heat exchangers, reduce engine noise, and mask exhaust odors, and which removes and treats condensate to further inhibit frosting and corrosion. Dispersion and condensate removal are achieved with exhaust gas distribution and condensate draining features incorporated into the exhaust system of the present invention, and with a fan compartment structure which promotes more complete mixing of exhaust gases and ambient air, while housing both the exhaust system and the outdoor heat exchanger.

Abstract: A heat engine driven heat pump system including a coolant fluid circulation subsystem further includes an automatic purge system to provide purging of air gases and vapors during initial filling and subsequent on-line operation to eliminate trapped and accumulated gases and vapors which decrease heat pump system efficiency and reliability, and interfere with waste heat recovery.

Abstract: A coolant fluid circulation subsystem for engine driven heat pump systems including a coolant fluid loop through the engine and a recouperator, and through a thermostatic control valve operable to convey and to modulate flow from a coolant reservoir during engine operation, with the coolant fluid being selectively switchable, between first or second heat exchangers in heat exchange relation with the indoor and outdoor ambient condition selectively. An auxiliary pump and coolant fluid heater are provided in the subsystem to increase the heat contained in the coolant fluid and to exchange heat to the indoor ambient condition.

Abstract: A coolant fluid circulation subsystem for engine driven heat pump systems including a coolant fluid loop through the engine and a recuperator, and through a thermostatic control valve operable to convey and to modulate flow from a coolant reservoir during engine operation, with the coolant fluid being selectively switchable, between first or second heat exchangers in heat exchange relation with the indoor and outdoor ambient condition selectively. An auxiliary pump and coolant fluid heater are provided in the subsystem to increase the heat contained in the coolant fluid and to exchange heat to the indoor ambient condition.

Abstract: Typical apparatus as shown in FIGS. 1 and 12 for indicating the relative positions in a given direction between a reference point (24,59) and a test point (29,68) spaced therefrom and movable relative thereto is useful for measurement of the magnitude and direction of static or dynamic torque in a shaft (8). Overlapping transparent reference (20,60) and test surfaces (25,61), either parallel disks (60,61) or coaxial cylinders (20,25) each having a relevant portion covered with a plurality of equally spaced lines oriented predominantly normal to the given direction and at an angle to each other, produce moire fringes (30) when illuminated (14,15). One of the surfaces (25,61), being flexible, is connected to the shaft (8) so as to flex in response to torque between the reference point (24,59) and the test point (29,68), causing a change in the angle between the lines on the two surfaces (20,25;60,61), and thus of the spacing (D) (FIG.