Refrigeration – Automatic control – Refrigeration producer
Reexamination Certificate
1999-03-31
2001-02-27
Wayner, William (Department: 2859)
Refrigeration
Automatic control
Refrigeration producer
C236S00100H, C374S029000
Reexamination Certificate
active
06192697
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a heat transfer measurement method and system. More particularly, the present invention relates to a method and system for measuring heat transfer in a transient environment, using a hybrid of active and passive techniques.
2. Description of Related Art
Though temperature measurements have long been used to study the flow of thermal energy in the design and optimization of heating and cooling systems, temperature is only a secondary variable. A complete understanding of the heat transfer profile in an environment requires accurate measurement of the heat transfer rate. However, due to the complex nature of thermal energy flow, the heat transfer rate is an extremely difficult quantity to accurately measure. Generally, heat transfer measurement techniques are known in the art that employ either an active or passive technique, but not both.
The active technique involves measuring the amount of power required to maintain either a constant temperature or power output for a surface in a given environment. The heat transfer rate can be calculated by determining the temperature of the surface, the temperature in the environment, and the amount of power provided to the surface. However, this technique has some significant shortcomings. In particular, the active approach requires a large and bulky power supply to maintain constant temperature or power output of the surface under extreme temperature conditions. In addition, this technique requires a complex and expensive temperature controller to assure a constant temperature of the surface in the transient environment.
The other method known in the art is the passive approach. This method involves initially altering the temperature of a surface and allowing the surface to transiently equilibrate. Using the passive technique, the heat transfer rate can be calculated with knowledge of the initial and final temperatures of the surface, the environment temperature, and the time or history between the initial and final temperatures (i.e., the time for the temperature of the surface to equilibrate with the temperature of the environment). Although the passive technique does not require a large power source, it provides limited data acquisition time and can result in difficult quantitative interpretation.
In view of the foregoing, there is a need for an improved method and system for measuring heat transfer in an environment.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a method and system that substantially obviate one or more of the limitations of the related art. To achieve these and other advantages, and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention includes a system comprising a probe including at least one element provided with at least one electrical lead (i.e., connector) extending from the probe. The at least one element is configured to change temperature of the element and to determine temperature of the element. The system also includes a power supply for providing electrical power to the element. In addition, an amplifier may be provided for amplifying a temperature signal received from the element. The system further includes a temperature monitor for receiving amplified temperature signals from the amplifier and for determining whether the temperature of the element corresponds to a first predetermined temperature or a second predetermined temperature. Additionally, a timing structure is provided for measuring the time elapsed from when the element reaches the first predetermined temperature to when the element reaches the second predetermined temperature. The system also includes a system controller for controlling the power supply and timing structure. The system controller receives signals from the timing structure and provides signals to the timing structure and the power supply.
In another aspect, the system for determining heat transfer in an environment includes a temperature sampler for receiving temperature signals from the amplifier and for measuring the temperature of the element at the beginning and the end of a predetermined period of time. Additionally, a system controller is provided for controlling the power supply and the temperature sampler. The system controller provides signals to the power supply and the temperature sampler and receives signals from the temperature sampler.
In a further aspect, the present invention includes a method for determining heat transfer in an environment with a probe including at least one element. The method includes determining temperature of the environment. Additionally, the method includes changing temperature of the element to increase the difference between the temperature of the element and the temperature of the environment. After the changing of the temperature, a first temperature of the element is determined. Next, the element is allowed to equilibrate (i.e., cool or heat) for a predetermined period of time towards the temperature of the environment. After the predetermined period of time, a second temperature of the element is measured. Finally, the heat transfer rate to or from the environment is calculated based on the first temperature, the second temperature, temperature in the environment, and the predetermined period of time.
In another aspect, the method includes changing the temperature of the element so that the element reaches a first predetermined temperature different from temperature of the environment. When the temperature of the element is changed, the first predetermined temperature is sensed. Next, the temperature of the element is allowed to equilibrate (i.e., cool or heat) towards the temperature of the environment. While the element is equilibrating (i.e., cooling or heating), a second predetermined temperature is sensed. A measurement is made of the time elapsed from when the first predetermined temperature is sensed to when the second predetermined temperature is sensed. Finally, the heat transfer in the environment is calculated based on the first predetermined temperature, the second predetermined temperature, temperature of the environment, and the measured time.
In yet another aspect, the probe includes one element configured to change temperature of the element and to determine temperature of the element.
In another aspect, the probe includes both a first element configured to change temperature and to measure temperature of the first element and a second element configured to measure temperature of the environment.
In another aspect, the invention includes a system for controlling the heat transfer rate in a climate controlled environment. The system includes at least one wall forming at least a partially closed environment. Additionally, a climate control sub-system is provided for changing temperature in the environment. The system also includes a heat transfer rate determining subsystem for determining heat transfer rate in the environment. The heat transfer rate determining sub-system includes at least one of the systems for determining heat transfer discussed above. Moreover, the system includes a climate controller for controlling the climate control sub-system. The climate controller receives input from the heat transfer rate determining sub-system and is configured to provide a predetermined heat transfer profile in the environment.
It is to be understood that the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.
REFERENCES:
patent: 4522512 (1985-06-01), Atkins
patent: 5921090 (1999-07-01), Jurewicz et al.
patent: 5946922 (1999-09-01), Viard et al.
patent: 0 279 865 (1988-08-01), None
patent: 0517 496A (1992-12-01), None
patent: 2 265 460 (1993-09-01), None
Goodwin Brian
Sahm Michael K.
Wardle David G.
Pace Salvatore P.
The BOC Group Inc.
Wayner William
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