Abstract: An improved tracer gas leak detection system and method for air inleakage testing of a turbine-condenser system quantified leak testing with two new elements: one, by providing discharge of a fixed, reproducible amount of tracer gas at a possible leak site, which is accomplished by controlling the flow rate, pressure and time interval of the discharge. Secondly, the total amount of tracer gas subsequently detected within the turbine-condenser is determined by integrating the detector response.

Abstract: A low-voltage space thermostat for controlling operation of a heating and cooling system is provided with integral circuit means for detecting the existence of an unacceptably high voltage potential between two wiring terminals therein. Such a high voltage potential exists when the power source in the system comprises two transformers connected out of phase with each other.

Abstract: A single assembly of a water heating system for heating the water and air in a room, and an electrochemical reactor which activates a gas alarm for human safety upon detection of a predetermined dosage of gas, such as, for example, a fatal dose of a gas such as carbon monoxide, and which detoxifies the gas.

Abstract: A cooling process and apparatus which utilizes the lower water vapor pressure above a fluid such as water-salt solutions of, for example, calcium chloride, lithium chloride, lithium bromide or mixtures thereof. Heat is then removed from the fluid by indirect contact with a circulating water stream in a heat exchanger. Water which has taken up heat from the fluid is expanded at reduced pressure to release water vapor and lower the temperature of the water. The water vapor is then absorbed in a salt solution having a higher temperature but a lower water vapor pressure than that of the released water vapor. The remaining water is recirculated to the heat exchanger.

Abstract: In a heat exchange vessel which conducts a hot, pressurized synthetic gaseous stream carrying particulate matter through a central heat exchange chamber, a safety system for monitoring pressures within the vessel. Said heat exchange vessel includes a shell surrounding a water wall, defining an annulus therebetween. Pressure sensing means communicated with the respective heat exchange chamber and said annulus connects to means for determining the pressure differential between said points. A purge gas source communicated with the monitor system maintains the latter free of internal passage blockage caused by accumulations of particulate matter.

Abstract: The invention relates to a process for the simultaneous exchange of heat and matter through a porous wall. A relatively hot gaseous mixture of two constituents passes through an exchange compartment by flowing along the first surface of a porous wall and is progressively cooled, which causes the condensation of a fraction of said mixture. This fraction is vaporized on the second surface of the wall in contact with a relatively cold gas. This process is useful for the fractionation of a mixture of two constituents of a gas, for example, of a mixture of pentane and heptane.

Abstract: Device for warming or defrosting products for injection or perfusion, particularly blood products, contained in hermetically sealed bottles or bags (10), comprising a cell (1), means making it possible to continuously introduce temperature-controlled water into the cell and possessing at least one inlet line (4) in which are fitted an adjustable thermostatic tap (2) connected on the one hand to a cold water distribution network (2a) and on the other hand to a hot water distribution network (2b), and a flow control valve (3), the cell being provided in its upper part with at least one overflow (5) for the flow of water, such that at least one bag or bottle (10) of product arranged in the cell (1) is submerged, the temperature-controlled water circulating around the bag or bottle.

Abstract: The ratio of the pressure change across a portion of the ventilation system of a hydrogen cooled electric power generator to the pressure increase across a reference blower, preferably the purity blower, is compared to a base ratio to generate an alarm when the difference in ratios exceeds a predetermined amount indicative of a failure within the ventilation system.

Abstract: Gas/liquid heat exchanger with condensation.It is presented in the form of blocks juxtaposed (1) within an enclosure (2) and in which two series of channels (3,4) are pierced, these blocks (1) being disposed within an enclosure (2), the space between the enclosure (2) and the central column which the blocks form being separated into two chambers (6,7), connected respectively to the gaseous phase supply circuit (10) and the other to the circuit (14) for the evacuation of the condensates formed.

Abstract: A variable volume air conditioning system of the type having a duct for distributing air to a room, a damper for regulating the flow of air through the duct, and a damper actuator responsive to damper drive control signals for controlling the damper. A thermostat located in the room provides a stat signal representative of a desired flow of air through the duct. An actual flow signal representative of the actual flow of air through the duct is provided by a sensor. The stat signal and actual flow signal are compared by a comparator which provides the damper drive control signals as a function of the comparison. A wire transmission line couples the actual flow signal from the sensor to the thermostat so that service personnel can easily monitor system performance.

Abstract: A portable compressed air cooling apparatus for a compressed air system of the type including an air compressor having a compressed air outlet port, a compressed air output unit, and a compresssed air supply line having a first end coupled to the compressed air outlet port of the air compressor and having a second end coupled to the compressed air output unit. An elongated tube is provided between the compressed air outlet port of the air compressor and the compressed air output unit so that all of the compressed air passing from the compressed air outlet port of the air compressor to the compressed air output unit will pass through the tube before passing to the compressed air output unit. A hollow tank surrounds at least a portion of the tube and a liquid coolant is sealed within the tank for cooling the compressed air as the compressed air passes through the tube.

Abstract: A proportion of the liquid metal flow passing through a fast reactor steam generator unit (SGU) is diverted past the outlet to a quiescent zone in the region of immersed tube-to-tubeplate welds at the water entry ends of the tubes, into which zone are given off any hydrogen bubbles which may result from a water leak into the liquid metal. The liquid metal in this zone is caused to flow through a weir system above which there is a gas space for collection of hydrogen, suitable means being provided for detection of hydrogen in this space. The hydrogen is entrained at the water inlet tube plate, the invention making use of the slow solution rate of hydrogen in sodium at lower temperatures prevailing in the quiescent zone at the water inlet end.

Abstract: A method and apparatus for heat and mass transfer is described that is applicable to: concentration, crystallization, purification, fractionation, stripping, absorption, and/or heat exchange for liquid media; drying for solid or gel media; and temperature and humidity modification for gas media. Generally, using a moving gas, such as air at a constant and atmospheric pressure, a continual change in a vapor-liquid equilibrium is created between proximate but continually changing gas and liquid temperatures within energy transferring chambers. Chamber wetting, implemented segmentedly, allows mass transfer into and from the moving gas. A forced temperature differential in each chamber causes heat transfer between chambers by means of thermally conductive partitions. This transfer can allow condensation causing further evaporation in the opposite chamber resulting in a recycling of energy.

Abstract: A troubleshooting apparatus counts the number of times an abnormality occurs whenever each diagnosed portion of an automobile air-conditioning system repeats an abnormal and a normal status, stores each diagnosed portion in which an abnormality is detected and the number of times the abnormality of each diagnosed portion occurs in a nonvolatile memory, recognizes each diagnosed portion having the number of times the abnormality exceeds a predetermined value at the time of troubleshooting as a fault, and recognizes each diagnosed portion having an abnormality that occurs at the time of troubleshooting as a fault. Abnormalities that occur in conjunction with the dismounting and remounting of diagnosed portions during checking processes are absorbed in the number of times the abnormality occurs within the predetermined value so that a wrong diagnosis can be avoided.

Abstract: A regenerative air heater is comprised of a matrix of heating surface elements contained in a compartmented housing with heat transfer being effected by alternately exposing the heating surface elements to hot gas and cooler air, thereby heating the exiting air stream. Un-burned products of combustion present in the gas may collect on the heating surface and, under certain operating conditions, ignite spontaneously in one or more local areas. In some instances, the local combustion can become severe enough to cause the heat transfer surface itself to burn, seriously damaging the heat exchanger. An elongated expansion element, made of a material having a high coefficient, of thermal expansion relative to the compartment structure, is used to sense the presence of a hot spot in any air heater compartment. The resulting thermal initiated expansion of the element activates a device to indicate the presence of a hot spot in the heat exchanger.

Abstract: A heat exchanger for condensing a vapor containing non-condensable gases comprises an inlet header for receiving said vapor and non-condensable gases, and a plurality of heat exchanger tubes arranged in a plurality of vertically spaced banks. One end of each tube is connected to the inlet header for receiving the vapor and the non-condensable gases in parallel; and the other end of each tube in a bank is connected to a separate header associated with each bank. Each separate header is vented for venting non-condensable gases therein to the atmosphere. The provision of separate headers for each bank of tubes prevents equalization of pressure between the banks thereby preventing back-flow and the creation of pockets of non-condensable gases in the tubes of a bank.

Abstract: A room temperature controlling apparatus used for an air conditioner includes a thermistor for detecting the temperature in a room, a variable resistor for setting a reference temperature for said room, a pyroelectric infrared sensor for detecting movement of a person in said room and outputting signals representative of the detection of the movement of said person, a room temperature modification circuit for modifying the room temperature detected by said thermistor based on the signals transferred from said pyroelectric infrared sensor, and a comparator for outputting a signal to control the operation of the air conditioner according to the reference temperature set by said variable resistor and the room temperature modified by said temperature modification circuit.

Abstract: A system for automatically controlling the buoyancy of a lighter-than-air craft by condensing water ballast from engine exhaust gases.

Abstract: A process of removing dust collected on the internal surfaces of a shell and tube type heat exchanger after passing a dust containing gas stream through the shell-side of a heat exchanger, by passing a heating fluid through the tube-side of the heat exchanger at a temperature sufficient to melt the dust particles, and collecting the melt at the bottom most portion of the heat exchanger in a melt collection device such as a pan or container.

Abstract: A detector (32) monitors infrared ray emissions from an air preheater (10) rotor (14) to detect a temperature rise that precedes a fire within air preheater (10) with each sensor output being processed independently by signal processing electronics. The instantaneous minus the average temperature of rotor (14) is calculated and compared to a variable trip level signal to determine whether a hot spot has been detected. The detector (32) scans across the face of rotor (14) until an initial hot spot is detected, whereupon the scanner motor (58) ceases operation thereby locating the scanner over the rotor radial position of the detected hot spot. If the same hot spot is detected on the next subsequent rotor pass, a hot spot alarm (60) is energized. If the hot spot is not detected on the next subsequent rotor pass, detector scanning is resumed by energizing scan motor (58).

Abstract: A power saving system for a hotel guest room has a keyboard operated control circuit that controls operation of an electrical load, such as a room air conditioner, and arms a door-window security circuit. When the guest enters the room, he disables the load control and security alarm system by actuation of a suitable contact on the keyboard. Prior to leaving the room, in order to secure it, he enables the security alarm system, and also the electrical load control, by making a suitable entry on the keyboard.

Abstract: Apparatus for analyzing air conditioning systems comprising a temperature probe adapted for manual placement at each of a plurality of preselected points in turn around the refrigerant loop to provide signals indicative of temperature at each point. Apparatus electronics are coupled by a cable to the temperature probe and includes facility for reading and storing each of the probe temperature measurements in turn. Information indicative of standards and ranges of temperature data for properly operating refrigeration systems of a number of models and manufacturers is prestored in apparatus memory. The system temperature readings are compared to each other and to the prestored data to diagnose a plurality of fault conditions and to display diagnosed fault conditions to an operator.

Abstract: A heat recovery system including a closed working fluid loop constituted by connecting an evaporating apparatus supplied with warm waste water, a steam turbine having an output shaft to be coupled to the load, and a condensing apparatus supplied with cooling water, works on the basis of a Rankine cycle and is adapted to utilize a non-azeotropic mixture as the working fluid.

Abstract: A microprocessor-based perimeter thermal energy control system regulates heating and cooling in the perimeter area of a building in accordance with instantaneous and integrated heat flow measurements and instantaneous temperature deviation measurements. Control of heat pumps and air conditioning units is provided as is automatic switching between heating and cooling. The inherent thermal parameters of the space are inductively determined and used by the system to continually self-adapt to the heat flow properties of the space. The gain of the heat flow based control system is varied automatically as a function of the deviation between the actual space temperature and the desired set point temperature. Morning recovery is initiated and regulated in response to instantaneous and integrated heat flow measurements and inductively determined thermal space parameters and produces a near linear stepwise change in the temperature of the space from night setback to occupancy temperature.

Abstract: A delayed response air conditioning/heating control system provides a detector which responds to a door or window left open, after a predetermined period of time, and which automatically resets to start time (maximum) if the door or window is closed prior to time of response; otherwise it disables the air conditioning heating system. The system has a wired, or anternatively a wireless, sensor with built-in delay and reset, and a receiver or detector with latching relay and manual relay reset control. If the air conditioning/heating system was operating at the time of disablement, a flashing light indicates this.

Abstract: A system of interconnecting a plurality of users of low grade thermal energy exchange has a number of users which are heat sources and a number of users which are heat sinks to balance heat flux. Heat is exchanged between a nontoxic primary heat transfer liquid and secondary heat transfer fluids for serving such users. The users are charged in proportion to the amount of heat transferred. Separate means are provided for selectively exchanging heat with the primary heat transfer liquid for maintaining the average temperature of the liquid within a desired temperature range. A municipal water main is a desirable source or sink of low grade thermal energy and nontoxicity of primary heat transfer liquid maintains the integrity of the water system.

Abstract: An air to air heat exchanger for ventilating buildings has the air streams maintained in direct contact with little mixing by tangentially introducing the air streams along cylindrical surfaces in opposite directions to form spiral, counterflows. Valves are provided to switch the flows for winter and summer operation.

Abstract: An improved muffler system for internal combustion engines recovers heat energy of exhaust gases by spraying a fluid into the exhaust stream in order to absorb the heat energy of the exhaust gases. The heated fluid is collected at the bottom of the muffler vessel and the stored heat energy is transferred to a second fluid via a counter-current liquid to liquid heat exchanger. The heat energy from the second fluid is then removed and utilized, for example, to condition passenger spaces.

Abstract: There is disclosed a method and apparatus for exchanging heat between a first fluid and a second fluid immiscible with said first fluid comprising the step of presenting one of said fluids in finely divided form for direct contact with the others. One fluid may be a molten metal which is sprayed or bubbled through the other.

Abstract: An exhaust gas containing sulfur trioxide is passed through a first heat exchanger which cools the gas to a temperature which is above the sulfur trioxide dewpoint, so that condensation of sulfur trioxide does not occur in the first heat exchanger, but below a material limit operating temperature of a second heat exchanger, which further cools the gas below the sulfur trioxide dewpoint, whereby the first heat exchanger is protected against corrosion and the second heat exchanger is protected against thermal damage.

Abstract: The disclosure involves a coefficient-of-performance (COP) diagnostic method involving the use of novel algorithms for determining performance manifested faults of vapor compression type refrigeration systems.

Abstract: An indicating instrument, for example a temperature controller, which is responsive to a parameter, such as temperature, of an associated system or apparatus comprises a first display arranged in an annular configuration and providing a visual indication of a set-point value of the parameter, a handwheel to adjust the set-point value to a different set-point value, and a second display providing a visual indication of an operating condition of the instrument or of the current value of the parameter. This second display is located within the annulus of the analogue set-point display. Preferably, the second display provides an indication of the difference between the current value of the parameter and the set-point value as shown by the marker. A series of LEDs may be used as the second display.

Abstract: A performance monitor generates a fouling factor which indicates the level of fouling of a heat exchanger having a heat exchange surface area and through which a heat exchange medium passes having a known specific heat. Temperature transmitters are utilized to obtain values for the input and output temperatures of the heat exchange medium as well as the temperature in the heat exchanger of a heat exchange fluid used to transfer heat to or from the heat exchange medium. Modules are used to generate a value for an actual heat transfer coefficient in the heat exchanger as a function of the temperatures, flow rate and constant parameters such as area and specific heat, for the heat exchanger. The actual heat transfer coefficient is compared with a nominal or original heat transfer coefficient to determine if any deterioration in the coefficients has occurred which reflects the fouling of the heat exchanger.

Abstract: In a sulfur condenser and degasser system associated with a Claus furnace, the condenser comprises a wound cross-countercurrent heat exchanger. Liquid sulfur is passed into the top of the condenser as reflux so that ascending sulfur droplets can be coalesced and the condenser can act as a rectifying column. The degassing is preferably carried out substantially simultaneously with the formation of liquid sulfur.

Abstract: A condenser including a plurality of condenser tubes through which a coolant is caused to flow, a device for injecting ferrous ions into the coolant before it passes through the condenser tubes to form a protective film on an inner surface of the condenser tubes, and a device for introducing sponge balls into the condenser tubes for cleaning their inner surfaces. The condenser has a by-pass line extending outside the body of the condenser, in parallel connection with the condenser tubes. The by-pass line has a monitor tube of the same material and size as the condenser tubes, so that the coolant flows through the monitor tube under the same conditions as the coolant flowing through the condenser tubes. The monitor tube is equipped with a device for measuring a polarization resistance of the monitor tube, and a device for sensing a fouling condition of the inner surface of the monitor tube.

Abstract: A water management system for heat exchange devices is disclosed which includes an aqueous based heat exchange liquid containing dissolved corrosion inhibitors and a fluorescent dye, conduit means adapted to circulate the heat exchange liquid between a source of heat, such as an engine, and a cooling device, such as a radiator, a liquid or solid concentrate containing measured amounts of the corrosion inhibitors and the fluorescent dye packaged in defined unit quantities, and a comparator calibrated to provide a visual indication of the concentration of the corrosion inhibitors in the liquid and, if the concentration falls below an established level, the number of units that must be added to restore the established level.

Abstract: A temperature sensor located at a region being monitored controls an output switch that in one position when ambient temperature is below a predetermined temperature applies current to only a first loop circuit and in another position when ambient temperature is at or above the predetermined temperature applies current to only a second loop circuit. Currents in the first and second loop circuits are measured by ferrods to determine whether an over-temperature condition at the region monitored has taken place. An alarm circuit connected to outputs of the ferrods generates an alarm signal in response to a negative transaction of current in the first loop circuit or a positive transition of current in the second loop circuit. A failure in either loop circuit accordingly is insufficient to disable the system. A solid state timer periodically opens the second loop circuit to repeat the alarm signal when the second loop circuit is closed until corrective action is taken.

Abstract: A sealed accumulator is positioned at a location remote from the conventional pressurized liquid cooling system of an internal combustion engine. An overflow conduit communicates between a high point in the system and the accumulator. A make-up conduit communicates between the accumulator and a low point in the system. A normally closed pressure valve, opening in response to system pressure exceeding a predetermined value, is in series with the overflow conduit. In series with the make-up conduit, is a normally closed one-way check valve. Minimum and maximum pressures within the accumulator are regulated respective relief valves. Optionally, a vent valve is installed at a high point for escape of air as coolant is introduced into the system.

Abstract: A hydraulic circuit branch of a cooling system in thermal contact with the stator winding of a hydraulic power generator is provided with a feed tube divided into two separate input tube sections. The downstream ends of the input tube sections are connected to respective multiplicities of subsidiary hydraulic circuit branches in the form of winding bars via a pair of semicircular manifolds. The current throughput through the winding bars is monitored by determining the difference between the rates of coolant flow through the approximately identical input tube sections. If the rates of coolant flow or throughputs in the input tube sections differ from one another by an amount which itself differs from a predetermined reference value by more than a preselected threshold, a warning signal is generated indicating that heat removal from the hydraulic power generator is being impaired.

Abstract: A condenser for separating solvent vapors from non-condensable gases. The condenser includes an outer shell, a middle shell inside the outer shell, and an inner shell inside the middle shell. The shells are coaxial and the middle shell is open at the bottom. Mixed solvent vapors and non-condensing gas pass downwardly through an annular space between the inner and middle shells. There is a condensate receiving chamber in the outer shell below the lower end of the middle shell. A cold trap is mounted in the upper portion of the condensate receiving chamber. Coolant is introduced into the cold trap to cool the cold trap. Helical tube means mounted on the cold trap receives the coolant from the cold trap. The helical tube means extends upwardly through the annular space between the inner and middle shells and discharges into an upper portion of the inner shell, and is removed from the inner shell. Condensate is withdrawn from the chamber in the lower portion of the outer shell.

Abstract: A hermetically sealed low pressure, low temperature cooling system for internal combustion engines which include a thermostat that operates at a predetermined temperature, typically 195.degree. F. Thermostatic control of engine operation temperature is maintained at or in relatively close proximity to this predetermined temperature thereby eliminating overheating and corrosive deterioration of the cooling system. Free coolant flow between the radiator and a small expansion reservoir is maintained at all times with the expansion reservoir positioned at the elevation of an outlet near the top of the radiator or slightly above this elevation. The system is provided with a transparent viewing cap for the radiator so that the level of liquid coolant can be observed at all times.

Abstract: Cost and weight of a heat transfer structure for a space vehicle can be reduced by an arrangement of redundant channels for the flow of coolant to heat radiating panels, micrometeroid resisting bumpers located adjacent the channels for preventing penetration by all but the most energetic micrometeroids, and a sensing and control arrangement for sensing the penetration of a coolant channel for shutting off that channel to prevent loss of coolant.

Abstract: The process consists in that two comparison tube sections (3; 4), which originate from a single condenser tube and of which one (3) is left in the corroded condition and/or the condition encrusted by mineral deposits and the other (4) is brought into the new condition by etching or other cleaning procedures, are conductively connected in series, and cooling water flows through them and they are heated from the outside in a condenser chamber in each case (1 and 2 respectively) by steam flows of equal power. The temperatures (t.sub.1, t.sub.2 and t.sub.3, t.sub.4 respectively) measured at the inlet and outlet positions of the comparison tube sections (3; 4), the measured values of the mass flow of cooling water (M.sub.w) and the steam temperatures (t.sub.f ; t.sub.b) and the heat flows (Q.sub.kf =Q.sub.kb) in the two condenser chambers (1 and 2 respectively) permit the determination of the thermal resistance (R.sub.

Abstract: The process consists in displacing a camera (15), provided with a sensitive support, parallel to the tubular plate (2) of the steam generator inside the water tank (3), successively taking photographs of the primary face (2a) of the tubular plate (2), making from the sensitive support, extracted from the water tank (3), pairs of photographic images of the ends of the tubes (8) flush with the tubular plate (2) with different angles of perspective, orienting the photographic images of the pairs in relation to one another to obtain a stereophotogrammetric view of the end of each of the tubes (8) to be checked, and making measurements and observations on the stereophotogrammetric view. The invention also relates to checking apparatus comprising a camera arrangement movable inside the water tank.

Abstract: An energy storage and conversion system utilizes unique heat exchange media for storing and transferring heat. In one embodiment, a refractory material is heated to the molten state by a solar furnace. The refractory material is stored in its molten form and metered to a direct-contact heat exchanger. It is fed into the heat exchanger in a plurality of streams that break into a plurality of droplets. The droplets flow through the heat exchanger in countercurrent relationship with a relatively inert gas such as argon or nitrogen. The gas is heated and expanded through an expansion engine to convert the thermal energy to mechanical energy which in turn can be utilized to produce electricity, for example. The refractory can be sufficiently cooled in the heat exchanger to fuse into beads, which can be easily recycled to the solar furnace.

Abstract: Ambient air (2) is canalized and cooled in a free space (4) delimited by a thermally insulated enclosure (1) and a radiating heat exchanger (3) of which the outer face (6) is heat-absorbing and the inner face (5) is heat-radiating. Air is then passed through a curtain of hygroscopic fibres (11) where water vapor condensates into liquid water which is evacuated through a conduit (14) and, once dried, air is heated by flowing at the inside (8) of a radiator (7) recovering thermal energy emitted by the face (5) of the heat exchanger (3) through a transparent thermally insulating volume (12). Dry air is then exhausted through a vent (9) to the atmosphere. Since air circulates naturally, it is possible to recover, autonomously and without any other energy supply, water contained in vapor form in the atmosphere of the implantation site.

Abstract: A steam generator in which the heat-carrying fluid is a liquid metal and the detection of leakages is carried out by sampling the liquid metal. The end of the steam generator through which the liquid metal enters comprises a tube plate (2), a thermal protection plate (10) and a hollow flow sill (22) constituting the end part of the bundle case (4). Tubes (20) for protecting the tubes (3) of the bundle are placed around each of the tubes (3) between the protection plate (10) and the tube plate (2), the space (17) between these two plates being closed on its periphery by a sleeve (15). The hollow sill (22) communicates with the space (17) through tubes (27) and with the inner volume or the bundle case (4). A liquid metal take-off device (31, 32) is placed in the hollow sill (22). The invention applies in particular to steam generators of fast neutron nuclear reactors cooled with liquid sodium.

Abstract: The room temperature control unit is provided with a switch for determining whether the room is vacant or occupied and if required with a switch for determining whether the room is cooled or heated, so that the room temperature is controlled while the room is vacant to be somewhat (e.g. 2.degree. C.) higher than a set temperature when the room is cooled, and somewhat (e.g. 2.degree. C.) lower than a set temperature when the room is heated. For that purpose, at least two common contacts are provided and they are connected to switch contacts in different ways so that one common contact is selected according to whether the room is vacant or occupied.

Abstract: A process controlling a thermal installation is described. The flow of a process liquid through a heat exchanger is achieved dependent upon two temperatures. One is the return temperature of the process liquid which, through the switching on and off or modulation of a circulation pump is maintained at a constant value. The other is the room or outside temperatures or the difference between these two temperatures, whereby during the deviation of a predeterminable limiting value the pump is also switched on and off or modulated. Since the supply temperature from a boiler has a constant temperature, for a central heating system the same amount of heat is drawn from each unit of heating water and thus the measure of the pump flow is sufficient to determine the actual heat consumption. Thereby the fair division of heating costs for each tenant according to actual amount consumed is made possible.

Abstract: A room temperature control system includes a transmitter-receiver unit for producing an acoustic standing wave pattern in a room and for producing a signal when that pattern is disturbed by motion in the room. A logic circuit provides timing signals and interprets a pattern disturbance signal to determine whether it evidences room occupancy. The timing and interpreting sequence is initiated by a switch which detects opening and closing of the room door. Temperature control by the room thermostat is permitted when the room is occupied and control within a wider range can be provided when it is not occupied.