Showing papers on "Temperature control published in 1995"

An application of electrothermal feedback for high resolution cryogenic particle detection

Abstract: A novel type of superconducting transition edge sensor is proposed. In this sensor, the temperature of a superconducting film is held constant by feeding back to its position on the resistive transition edge. Energy deposited in the film is measured by a reduction in the feedback Joule heating. This mode of operation should lead to substantial improvements in resolution, linearity, dynamic range, and count rate. Fundamental resolution limits are below ΔE=√kT2C, which is sometimes incorrectly referred to as the thermodynamic limit. This performance is better than any existing technology operating at the same temperature, count rate, and absorber heat capacity. Applications include high resolution x‐ray spectrometry, dark matter searches, and neutrino detection.

Inline thermo-cycler

Abstract: Thermo-cycling for biological material is provided by a channel such as a capillary tube extending through a series of temperature control elements. Each temperature control element maintains the adjacent portion of the channel at a desired temperature. Fluid to be processed is introduced into the tube through the inlet and flows, preferably through capillary action, to the outlet. The temperature of the fluid changes as it passes each temperature control element and is thus thermo-cycled through a predetermined sequence of temperatures.

A thermostat system having an optimized temperature recovery ramp rate

Abstract: An adaptive recovery method for a setback thermostat using the intersection of the space temperature with a sloped recovery temperature line which approximates the change in temperature as a function of time during recovery of the temperature controlled space from a setback temperature, to determine the time at which recovery to the occupancy temperature should begin. The thermostat starts recovery when the current space temperature crosses the recovery temperature line. A useful feature of the apparatus and method which implement the invention, computes and constantly updates the slope of the temperature recovery line. The update of the temperature recovery line slope is based on miss time, i.e., the time between actually achieving the desired next set point temperature and the next set point time associated with the next set point temperature, the space temperature, the outdoor air temperature, the temperature recovery ramp rate during the previous recovery period, and the current and past thermal time constants. If the heating or cooling load on the space changes, the current space temperature will cross the recovery temperature line at a different time, causing recovery to start at a time more compatible with the current heating or cooling load in order to complete recovery at or near the desired time. Variables may be added to the system.

Temperature control with stored multiple configuration programs

Abstract: A thermostat which is configurable to be used with conventional fossil fuel furnaces, electric furnaces, heat pumps and other air conditioning equipment and fans. A setup program is included which requires an installer to enter data specific to the type of HVAC plant installed in the building with the thermostat.

Temperature Control of Multi-Product Semi-batch Polymerization Reactors

Abstract: Abstract This paper considers the temperature control of semi-batch polymerization reactors in which some of the following issues must be considered: (i) production of multiple products in the same reactor; (ii) changing heat transfer characteristics, during a batch and from batch to batch; (iii) time varying and nonlinear reaction rate due to changing monomer concentration and diffusion controlled termination reactions (gel effect); (iv) the absence of detailed kinetic models for the reactors. The industrial challenge problem published by Chylla and Haase [Chylla, R. W. and Haase, D. R. (1993) Temperature control of semi-batch polymerization reactors (with corrected updates). Comput. Chem. Eng. 17, 257–264) is used as the simulation basis for evaluating these problems. A nonlinear adaptive controller consisting of a nonlinear controller (based on differential geometric concepts) coupled with an extended Kalman filter (which uses only readily available data and knowledge) is shown to provide excellent control in all the above situations. In particular, the on-line estimation is critical for the strong performance of the nonlinear controller over a broad range of conditions. PID controllers with feedforward terms can perform well at one set of conditions, however, they require retuning as conditions and products change.

Temperature control system with thermal capacitor

Abstract: An improved thermoelectric temperature control system for selectively heating or cooling a temperature control fluid to be provided through an exit conduit to an external thermal load and returned to the system through an inlet conduit. The system having at least a first liquid heat exchanger, a thermoelectric module in thermal conductivity with the liquid heat exchanger, a heat sink in thermal conductivity with the thermoelectric module, a pump and connecting conduits to move the temperature control fluid from the inlet conduit through the pump and liquid heat exchanger to the exit conduit and power and control electronics to activate the pump and thermoelectric module. The improvement comprises a thermal capacitor connected for fluid communication with the external thermal load and the thermoelectric temperature control system to provide thermal wattage to the external thermal load via the temperature control fluid in addition to the thermal wattage provided to the external thermal load by the thermoelectric temperature control system during the real-time use of the thermoelectric temperature control system. An alternate embodiment includes a liquid-to-liquid heat exchanger system to improve the efficiency of the system.

Multiprobe surgical cryogenic apparatus

Abstract: A cryogenic surgical apparatus comprises: a) a plurality of probes, each having a contact surface, each of which probes is suitable for creating fast temperature changes at the said contact surface; b) temperature generation means, coupled to each of the said probes, being capable of creating cryogenic and above 0° C. temperatures at the said contact surface of the said probe; and c) temperature control means, to control the said temperature generation means.

Power control circuit for improved power application and temperature control of low voltage thermoelectric devices

Abstract: A power control circuit for improved temperature control of thermoelectric devices to maintain the temperature of thermoelectric devices at a set point. The circuit includes a rectifying device to provide rectified alternating current when receiving an input from an electrical power source; a flyback power supply to supply a DC voltage to the thermoelectric device; a switching device to modulate the rectified alternating current across the primary of the flyback transformer; sensor circuitry to monitor the temperature of the thermoelectric device; and a programmable control device to receive an output from the sensor circuitry and provide a control signal to the switching device, the control signal being determined by the difference between the sensed temperature of the thermoelectric device and the desired set point to allow the DC voltage to the thermoelectric device to bring the temperature of the thermoelectric device to the set point and maintain the temperature of the thermoelectric device at the set point.

Temperature Rise in a Battery Module with Constant Heat Generation

Abstract: A three-dimensional battery module in the shape of a block is taken to generate heat uniformly throughout The temperature rise as a function of time is worked out based on equations for heat conduction in solids After appropriate nondimensionalization, the maximum temperature rise depends on the thermal aspect ratios (defined herein) By a superposition integral, the method can be extended to a time-dependent heat-generation rate, as appropriate for a driving profile

Hot and cold water mixing discharge device

Abstract: An automatic temperature control means 16 for automatically generating a mixed warm water of prescribed temperature by mixing an introduced hot water from a hot water inflow passage 14 and an introduced cold water from a cold water inflow passage 12 with each other at a flow rate ratio corresponding to the prescribed temperature, and a flow rate control means 19 for regulating the temperature of the discharged mixed warm water by mixing it with a hot or cold water introduced from the hot or cold water inflow passage 14 or 12 through a by-pass 18 around the former means are provided. As a result, mixed warm water of desired temperature can be easily obtained by manipulating the flow rate control means 19.

Thermal Stability of Ceramic Materials in Microwave Heating

Abstract: Thermal stability was examined theoretically for various commercial grades of alumina heated by microwave energy. The critical temperature for thermal runaway was evaluated as a function of Biot number and ambient temperature, employing various functional forms of the dependence of dielectric loss with temperature. Field-temperature relationships were derived for the limit of small temperature gradients in the specimen. Finite difference methods were used under conditions where significant temperature gradients were sustained in the specimen. The critical temperature approached limiting asymptotes for the extremes in Biot number, with smooth variation in the intermediate regime. Stability diagrams were constructed which denote regions of stability and their dependence on important system parameters. The effects of ambient temperature on critical temperature were determined analytically and compared with experimental observations on heating alumina fiber bundles by a hybrid configuration utilizing an external suseptor. The results have implications for temperature control near the critical temperature and the design of hybrid heating systems.

Multipoint temperature control during hyperthermia treatments: theory and simulation

Abstract: A real-time multipoint feedback temperature control system has been designed and implemented with an ultrasound phased-array applicator for hyperthermia. The control parameters are the total power available from the supply and the dwell times at a sequence of preselected heating patterns. Thermocouple measurements are assumed for temperature feedback. The spatial operator linking available heating patterns to temperature measurements is measured at the outset of the treatment and can be remeasured on line an adaptive implementation. A significant advantage of this approach is that the controller does not require a priori knowledge of either the placement of the thermocouples or the power distribution of the ultrasound heating patterns. Furthermore, the control loop uses a proportional integral (PI) gain in conjunction with a singular value decomposition (SVD) of the spatial transfer operator. This approach is advantageous for robust implementation and is shown to properly balance the power applied to the individual patterns. The controller also deals with saturation in the inputs without integrator windup and, therefore, without temperature overshoot. Here, the authors present the theoretical formulation and representative simulation results of the proposed controller. The control algorithm has been verified experimentally, both in vitro and in vivo. A subsequent paper describing these results and the practical implementation of the controller will follow. >

Regional observability of a thermal process

Abstract: The realization of a ceramic protector covering the subregion of a substrate and using chemical vapor deposition techniques needs the temperature field in the deposition zone to be controlled. A feedback control of this temperature is based on the knowledge of the temperature in the considered subregion. The difficulty occurs because measurements can only be obtained out of the deposition zone. The purpose of this paper is to give an original approach for the reconstruction of the state in the deposition subregion. >

Analytical determination of PID coefficients for temperature and humidity control during cooling and dehumidifying by compressor and evaporator fan speed variation

Abstract: A linearized analysis of temperature and relative humidity control using proportional-integral-differential (PID) controls to vary compressor motor speed and evaporator fan speed enables analytical determination of suitable PID coefficients. The PID coefficients are related to refrigeration system performance parameters and the volume of the conditioned space. Analytical determination of coefficients may eliminate or supplement trial-and-error methods. System response characteristics--damping ratios and periods--are related to PID coefficients, sampling intervals, performance parameters of a refrigeration system, and the volume of a conditioned space. Two control strategies are possible in order to control space temperature and relative humidity simultaneously. One strategy controls temperature by varying compressor speed and controls relative humidity by varying evaporator fan speed. The other strategy controls temperature by varying evaporator fan speed and controls relative humidity by varying compressor fan speed The first strategy was successfully implemented experimentally as well as by simulation. The second strategy was not successfully implemented due to an adverse interaction between the two control systems.

Temperature regulation with neural networks and alternative control schemes

Abstract: In this article, we compare the neuro-control algorithm to three other control algorithms: fuzzy logic control, generalized predictive control, and proportional-plus-integral control. Each of these four algorithms is implemented on a water bath temperature control system. The four systems are compared through experimental studies under identical conditions with respect to set-point regulation, the effect of unknown load disturbances, large parameter variation, and variable deadtime in the system. It is found that the neurocontrol system compares well with the other three control systems and offers encouraging advantages. From the results of the experimental studies, however, the best characteristics of each of these different classes of control systems may be combined for realizing a more efficient and intelligent control scheme. >

Plasma sputter etching system with reduced particle contamination

Abstract: A plasma processing system for sputter etching a substrate with reduced particle contamination comprises processing chamber (10) having an interior surface (18) which defines a processing space (19). An electrical element (24) couples energy into the processing space (19) for etching a substrate (20). A heating device (44) is coupled to the reactor for controllably heating the processing chamber interior surface (18) to a selected temperature. The heating device (44) is controlled by a temperature control circuit (48) which turns the heating device (44) to an ON state to heat the processing chamber (10) to a selected temperature when the plasma is extinguished. The selected temperature is related to the temperature of the processing chamber (10) during plasma generation such that the interior surface is maintained at a relatively constant temperature before, during and after processing to prevent flaking of sputter material from the interior surface and generation of contamination particles within the processing space.

Temperature and humidity control during cooling and dehumidifying by compressor and evaporator fan speed variation

Abstract: The accurate control of temperature and relative humidity during cooling and dehumidifying air-conditioning processes may be achieved by compressor and evaporator fan speed variation. Proportional-integral-differential (PID) control methods are shown to be suitable for attaining compressor and evaporator fan speeds such that the sensible and latent components of the refrigeration system capacity equal the sensible and latent components of the system load. The feasibility of the control method has been verified experimentally. A numerical model of an environmental control system, including refrigeration, space, and PID control subsystems, has been developed. The model is suitable for determining system response to variations of PID coefficient values and to variations of system loads.

Direct digital control thermostat

Abstract: An electronic digital thermostat is disclosed which is capable of use in a pneumatically controlled temperature control system of the type which has a pneumatic supply line which extends to various components of the control system and wherein the control elements of the system are controlled by varying the control pressure that is communicated to such elements. The thermostat is capable of operating in a LAN system environment, and can be retrofitted into unit ventilators and the like as a substitute for a conventional pneumatic thermostat. The thermostat has a processing means that enables sophisticated control to be achieved.

Etch profile shaping through wafer temperature control

Abstract: In a method of etch profile shaping through wafer temperature control during an etch process wherein deposition of a passivation film is temperature dependent, a gap between a semiconductor wafer to be etched and a cathode is pressurized at a first pressure, and the pressure in the gap is changed to a second pressure at a predetermined time during the etch process, thereby altering heat transfer from the semiconductor wafer to the cathode. The temperature of the wafer is adjusted one or more times during an etching process to control profile shaping of deep trenches, contact holes and shapes for mask opening shaping during the etch process.

Automatic temperature control method and apparatus for an automotive vehicle

Abstract: An automatic interior temperature control system for an automotive vehicle capable of controlling heat flux in response to changes in ambient temperature, outlet temperature, sun load and air flow by taking into account the relationship between these four variables in accordance with thermodynamic principles wherein an adjustment in heat flux corrects interior temperature error.

Bimodal electric vehicle battery system

Abstract: The capacity of a nickel hydroxide based battery is increased when recharge is carried out at a much lower temperature than its discharge. In the instance of a vehicle (70A) including a load (72) powered by a nickel oxide-hydrogen battery (74A), a generator (78A) is provided for recharging the battery. A switch (102) is selectively movable between a first position electrically coupling the battery to the load for operating the load and a second position electrically coupling the battery to the generator for recharging. Temperature control apparatus (104) maintains the temperature of the battery at a first temperature in the range of approximately 10°C to 50°C when the battery is electrically coupled to the load and is operable for maintaining the battery at a second temperature substantially lower than the first temperature and in the range of approximately 10°C to 30°C when the battery is electrically coupled to the generator. When the battery is used to propel the vehicle, the temperature control apparatus may include a stationary heat exchanger external to the vehicle to which the battery can be coupled for cooling and an external source of EMF may also be provided to which the battery can be coupled for recharging.

Temperature control method for a heating/cooling system

Abstract: A temperature control method and apparatus therefor controls an air temperature in a room by determining an error temperature between a set temperature and an actual room temperature. An auxiliary reference calorie is initially set as a previous state calorie value, an error calorie associated with the detected error temperature is determined by PID operation and a current calorie value in determined by adding or subtracting the previous state calorie value to/from error calorie, and the room temperature is brought to the set temperature using the current calorie value.

A fuzzy logic and rough sets controller for HVAC systems

Abstract: This paper describes an HVAC (heating, ventilating and air conditioning) system controller which employs a control algorithm using either fuzzy logic reasoning or rough set theory. The controller deduces the appropriate control outputs from sensor readings. The system is capable of controlling temperature and humidity. To maintain temperature at the reference point, the controller adjusts the flow of hot water into a heating coil for heating operation and the flow of chilled air through an air duct for cooling operation. To control humidity, the controller turns on and off a humidifier.

Image forming apparatus, control method for controlling the same and temperature control apparatus

Abstract: An image forming apparatus includes a fixing unit having a heat source, a temperature detecting unit for detecting a temperature of the fixing unit, an initial operation necessity detecting unit for determining whether an initial operation should be performed in the image forming apparatus, an initial operation selecting control unit for selecting an initial operation from among a plurality of predetermined initial operations based on the temperature detected by the temperature detecting unit when the initial operation necessity detecting unit detects that the initial operation should be performed, and a control unit for controlling the fixing unit so that the fixing unit performs the initial operation selected by the initial operation selecting control unit. Furthermore, a temperature control apparatus includes a determination unit for determining, based on the detected temperature of the body, whether the temperature of the body should be increased or decreased, a temperature increasing control unit for applying an AC voltage from the AC power supply to the heater so that the temperature of the body is increased when the determination unit determines that the temperature of the body should be increased, and a temperature decreasing control unit for applying to the heater a pulse-shaped AC voltage which is repeatedly turned on and off at a frequency so that the temperature of the body is decreased when the determination unit determined that the temperature of the body should be decreased, the frequency being generally not perceived by people.

Temperature control system and kneading-mixing extrusion apparatus having the temperature control system

Abstract: Disclosed is a temperature control system and a kneading-mixing extruder apparatus implementing the temperature control system. The temperature control system includes a flow passage formed in a stationary disc having a plurality of holes provided in a kneading mechanism of the extruder apparatus, a fluid supply device for supplying temperature-adjusted fluid into the flow passage and a temperature control device for setting the temperature of the stationary disc to a desired target temperature.

Temperature control in a portable analytical instrument

Abstract: Sample analysis in a portable analytical instrument, preferably in the form of a gas chromatograph, benefits from temperature control of one or more zones in the instrument by way of thermal energy developed from an energy reservoir. In a preferred embodiment, analytical instrument performs chromatographic analysis and the selected zone comprises a temperature-controlled thermal chamber, or oven (124) which includes a heating unit (118), a temperature sensor (128), and a cooling unit (130). A separation column column (118) is positioned within the oven (124). The energy reservoir comprises a first reservoir (125) of heating fluid in the form of a compressed light hydrocarbon, a second reservoir (126) of a compressed inert gas, or a combination thereof. A controlled temperature in the oven (124) resulting from the operation of the heating unit (118) and/or cooling unit (130) may be effected in response to a control signal generated by a computer (122). A sample mixture passing through the column (118) is thereby exposed to a desired temperature profile according to a selected program so that the sample (111) will separate into its components for subsequent detection by a detector (124).

Optimal indoor temperature control using a predictor

Abstract: This article deals with optimal control of the indoor temperature in a building. The control system attempts to find an economic optimum to supply heat to the building with the use of a predictor for the indoor temperature, while maintaining a comfortable temperature in the building. A general control structure is described that uses a linear objective function, which is minimized by linear programming. This general control structure is applied to a specific test facility called passive climate system, whose main feature is that it uses natural ventilation by means of adjustable windows for cooling purposes. This article also describes some field tests with the optimal predictive control system applied to the passive climate system. >