US3643457A - Frost detector for refrigeration system - Google Patents

Frost detector for refrigeration system Download PDF

Info

Publication number
US3643457A
US3643457A US91299A US3643457DA US3643457A US 3643457 A US3643457 A US 3643457A US 91299 A US91299 A US 91299A US 3643457D A US3643457D A US 3643457DA US 3643457 A US3643457 A US 3643457A
Authority
US
United States
Prior art keywords
duct
airflow
coil
bypass
frost
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US91299A
Inventor
Charles L Winkler
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
CBS Corp
Original Assignee
Westinghouse Electric Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Westinghouse Electric Corp filed Critical Westinghouse Electric Corp
Application granted granted Critical
Publication of US3643457A publication Critical patent/US3643457A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
    • F25D21/00—Defrosting; Preventing frosting; Removing condensed or defrost water
    • F25D21/02—Detecting the presence of frost or condensate
    • F25D21/025—Detecting the presence of frost or condensate using air pressure differential detectors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F5/00—Air-conditioning systems or apparatus not covered by F24F1/00 or F24F3/00, e.g. using solar heat or combined with household units such as an oven or water heater
    • F24F5/0007—Air-conditioning systems or apparatus not covered by F24F1/00 or F24F3/00, e.g. using solar heat or combined with household units such as an oven or water heater cooling apparatus specially adapted for use in air-conditioning
    • F24F5/001—Compression cycle type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
    • F25D21/00—Defrosting; Preventing frosting; Removing condensed or defrost water
    • F25D21/02—Detecting the presence of frost or condensate

Definitions

  • PATENTS provide a defrost initiation signal to the refrigeration apparatus and the preferred airflow velocity sensing device is an lg; g p f air-cooled electrical resistor connected in a bridge circuit.
  • frost detector systems uses a bypass duct connected to the main airflow duct on each side of the evaporator coil in the main duct so that when frost builds up on the coil, an increased airflow velocity occurs in the bypass duct and a suitably calibrated airflow velocity sensor provides the defrost signal when the airflow velocity in the bypass duct is such as to indicate an undesirable amount of frost on the coil.
  • a difficulty with the aforementioned frost detection system is that the fixed calibrated airflow sensing device could provide a defrost signal when there are changes in airflow velocity that are not due to frost accumulation on the coil such as for example a deliberate change in airflow velocity by changing the blower speed or the like.
  • the refrigeration system evaporator coil is positioned in a main airflow duct having a blower in its inlet side and a constriction in its outlet side downstream from the coil.
  • a first bypass duct is connected to the main duct on each side of the coil and a second or reference bypass duct is connected to the main duct on each side of the constriction in the outlet.
  • the airflow velocity in the first bypass duct will increase with the accumulation of frost on the coil assuming a particular fixed blower capacity but will also change with changes in blower speed.
  • the airflow velocity through the second bypass duct around the constriction in the outlet of the main duct will be proportional to the total mass flow rate and therefore may increase or decrease with corresponding changes in blower speed and the like but will not increase with buildup of frost and on the contrary, will decrease with buildup of frost.
  • a defrost signal can be obtained that will accurately correspond to the given amount of frost buildup on the coil irrespective of the randomness of the frost buildup or of changes in blower speed or the like.
  • the airflow velocity sensor in each bypass duct is an air-cooled electrical resistor connected in a resistance bridge circuit. In order to maximize the sensitivity of the air-cooled sensing resistors in the system, the range of air velocities through the bypass ducts may be adjusted by throttle valves if desired.
  • FlG. l is a sectional elevation of an air-cooled refrigeration system having the frost detecting arrangement of the invention.
  • FIG. 2 is a schematic of the bridge circuit of the invention.
  • the evaporator coil lltl is shown to be positioned within a main airflow duct 11 having a blower fan 12 in the inlet side thereof and a constructed outlet side 13.
  • a first bypass duct 15 is connected to the main duct 11 on each side of the evaporator coil as shown at 16 and 17 respectively.
  • An airflow velocity sensing device lltl is located within the first bypass duct 15 and a throttle valve 19 may be provided to control the range of air velocities through the bypass duct 15 if desired.
  • a second bypass duct 20 which is a reference bypass duct is connected across the constriction in the outlet side of the main duct lllr It will be noted that the constriction for the main duct 11 is formed by the converging duct wall 25 to which one end 26 of the reference bypass duct 20 is connected. The other end 27 of the reference bypass duct 20 is connected to the constricted outlet side 12 of the main duct 11.
  • An airflow velocity sensing device 23 is located within the reference bypass duct 20 and if desired a throttling valve 24 may also be provided to control the range of airflow velocities passing through the reference bypass duct 20.
  • the airflow velocity in the first bypass duct l5 will increase when frost builds up on the evaporator coil It) to impede or block the flow of air from the blower 112 through the main duct 11.
  • any change in the main flow velocity due to a change in blower fan speed 12 will also change the flow velocity in the first bypass duct 15. Therefore if the flow-rate sensor 18 is calibrated to provide a signal for a particular flow velocity, a false defrost signal could be obtained when the flow velocity increases in the bypass duct 15 due to an increase in speed for the blower fan 12.
  • a reference bypass duct 20 is mounted across the constriction in the outlet 13 of the main airflow duct 11.
  • the static pressure drop across the constriction varies approximately as the square law of the total mass airflow velocity, as it does across a well-known Venturi flow meter.
  • the reference duct flow velocity being a square root law of the static pressure drop, will therefore be proportional to the total mass flow velocity.
  • a defrost signal can be obtained which will indicate or detect the buildup of frost on the evaporator coil 10 regardless of changes in main airflow provided by the blower fan 12 and regardless of the randomness ofthe frost buildup on the coil 10.
  • the invention in its broadest sense is not limited to a particular type of airflow velocity sensor to be used in the bypass ducts 15 and 20, the preferred form of the invention employs air-cooled temperature sensitive resistors in a re sistance bridge circuit.
  • the airflow temperature sensitive resistor 18 in the first bypass duct 15 is connected in a resistance bridge circuit with the adjustable resistor 30, fixed resistor 31 and the airflow sensing temperature sensitive resistor 23 in the reference bypass duct 20.
  • Each of the temperature sensitive resistors 18 and 23 may preferably have a posi tive temperature coefficient although the invention is not limited to the use of such resistors since it would be obvious to anyone skilled in the art that other forms of temperature sensitive resistors such as those having; negative temperature characteristics may also be used.
  • a direct current power supply 33 is connected to the input terminals of the resistance bridge circuit and a defrost signal can be obtained by an unbalance of the bridge across the output terminals 34 and 25.
  • the adjustable resistor 30 is adjusted to balance the bridge for no output signal when the airflow rates sensed by the sensing resistors 18 and 23 are of the order corresponding to a condition of less than the undesired amount of frost on the evaporator coil 10.
  • frost has built up on the evaporator coil 10 to an undesired amount the increase in flow velocity through the first bypass duct 15 relative to the flow velocity sensed by the reference bypass duct 20 would change the resistance of the sensing resistor 18 relative to the sensing resistor 23 such as to unbalance the bridge and provide a defrost initiation signal across the bridge output terminals 34 and 35.
  • the throttle valves 19 and 24 may be provided in the respective bypass ducts l5 and 20. It should now be obvious to anyone skilled in the art that by suitably adjusting the throttle valves 19 and 24 and by suitably adjusting the bridge balancing resistor 30 a desired sensitivity and range of operation for the frost detector of the invention will be obtained.
  • each of the bypass ducts l5 and have cross-sectional areas considerably less than the cross-sectional area of the main duct 11 including the cross-sectional area of the constricted outlet 13 of the main duct 11. This is of course desirable in order to prevent either bypass duct from effectively shunting the evaporator coil or the system and is also desirable in improving the sensitivity of the system.
  • the apparatus for utilizing the defrost signal generated across the bridge output terminals 34, 35 since any well-known defrosting apparatus may be used and such apparatus is not a part of the present invention.
  • reference bypass duct 20 is shown to have one end 21 connected along the converging constriction wall 25 of the duct 11, it should be understood that the end 21 of the reference bypass duct 20 may be connected at any point along the main duct 11 upstream from the constricted outlet 13.
  • a frost detector for an air-cooling refrigeration system comprising, a main airflow duct, an evaporator coil substantially enclosed in said duct, means to force air to be cooled through said duct and coil from an inlet side to an outlet side of the duct, the outlet side of said duct having a constriction to reduce the cross-sectional area of the duct, a first bypass airflow conduit connected to said duct on each side of said coil ahead of the constriction of the duct, a second bypass reference airflow conduit connected to the outlet side of said duct between spaced points along the constriction of the duct, said first and second bypass conduits having cross-sectional areas considerably less than any cross-sectional areas of the duct, a respective airflow velocity sensor in each of said first and second bypass conduits, and means to compare the airflow velocity sensed by each sensor in the respective bypass conduits so that a change in airflow velocity through said coil due to the accumulation of frost on said coil may be detected regardless of variations in operation of the means to force air through the duct
  • each sensor is comprised of an air-cooled electrical resistor, and each sensor resistor is connected in a resistance bridge circuit to compare their changes in resistance due to changes in airflow through the respective bypass flow sensing conduits.
  • each of said bypass conduits is provided with a variably controlled airflow throttle to facilitate the comparison of sensed changes in airflow through the respective bypass conduits.
  • each sensor is comprised of an air-cooled electrical resistor, and each sensor resistor is connected in a resistance bridge circuit to compare their changes in resistance due to changes in airflow velocities through the respective bypass conduits.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Defrosting Systems (AREA)

Abstract

A frost detector for an air-cooling refrigeration system having an evaporator coil mounted in a main airflow duct is comprised of a first bypass duct connected to the main duct on each side of the coil and a second reference bypass duct connected to each side of a constriction in the outlet side of the main duct downstream from the coil. Signals from airflow velocity sensing devices in each bypass duct are compared to provide a defrost initiation signal to the refrigeration apparatus and the preferred airflow velocity sensing device is an air-cooled electrical resistor connected in a bridge circuit.

Description

Edited Wrinkles Feb. 22, 1W7? [54] IFRQST DE'lFlEQTUR lF UR 3,377,817 4/1968 Petranek ..62/140 REFRKGERATMUN YST1EM 3,423,222 911369 Sutton, Jr. et a1 ....62/l51 3,4 l l 70 Lorenz ..62/140 [72] Inventor: Charles IL. Winkler, Pittsburgh, Pa. [73] Assignee: Westinghouse Electric (Importation, Pitt- Primary Emmif'er Wmiam ODea Sburgh, Pa Assistant Exammer--P. D. Ferguson Attorney-F. H. Henson and F. E. Blalce [22] Filed: Nov. 20, 1970 21 Appl. No.: 91,299 [57] Amsmm A frost detector for an air-cooling refrigeration system having an evaporator coil mounted in a main airflow duct is coma! "62/13 prised of a first yp duct connected to the main duct on each side of the coil and a second reference bypass duct con- [58] Freid oi Search ..62/140, 151, 340/234 nected to each Side of a constriction in the Outlet side of the [56] References Cited main duct downstream from the coil. Signals from airflow velocity sensing devices in each bypass duct are compared to UNITED STATES PATENTS provide a defrost initiation signal to the refrigeration apparatus and the preferred airflow velocity sensing device is an lg; g p f air-cooled electrical resistor connected in a bridge circuit. utton, r. et a. 3,362,183 1/1968 Sutton, Jr. ..62/1 40 41 Claims, 2 Drawing Figures PAIENIEUHB 2 2 4972 3,, 6 3 5 Y HG. l
v |NV ENTOR WITNESSES C. L. Wmkler may on game) ATTORNEY BACKGROUND OF THE INVENTION Frost detection systems for refrigeration and air conditioning systems of the type having evaporator coils in a main airflow duct to detect the buildup and accumulation of frost on the evaporator coil to thereby provide a defrost signal to initiate a defrosting of the coil are well known. One of the most common frost detector systems uses a bypass duct connected to the main airflow duct on each side of the evaporator coil in the main duct so that when frost builds up on the coil, an increased airflow velocity occurs in the bypass duct and a suitably calibrated airflow velocity sensor provides the defrost signal when the airflow velocity in the bypass duct is such as to indicate an undesirable amount of frost on the coil. A difficulty with the aforementioned frost detection system is that the fixed calibrated airflow sensing device could provide a defrost signal when there are changes in airflow velocity that are not due to frost accumulation on the coil such as for example a deliberate change in airflow velocity by changing the blower speed or the like.
PRIOR ART Reference may be made to the U.S. Pat. No. 3,355,904, to Sutton, Jr. et al., issued Dec. 5, 1967, which discloses a refrigeration system frost detector using differential fluid velocity sensing in an arrangement which however does not provide the particular reference bypass duct arrangement of this invention which is located across a constriction of the outlet duct in a manner to assure proper tracking of the variable airflow velocity sensing devices over all of the possible variable conditions of operation including changed blower speeds, randomness of frost buildup on the coil, and changing temperature ambients or the like.
SUMMARY In accordance with the invention, the refrigeration system evaporator coil is positioned in a main airflow duct having a blower in its inlet side and a constriction in its outlet side downstream from the coil. A first bypass duct is connected to the main duct on each side of the coil and a second or reference bypass duct is connected to the main duct on each side of the constriction in the outlet. The airflow velocity in the first bypass duct will increase with the accumulation of frost on the coil assuming a particular fixed blower capacity but will also change with changes in blower speed. The airflow velocity through the second bypass duct around the constriction in the outlet of the main duct will be proportional to the total mass flow rate and therefore may increase or decrease with corresponding changes in blower speed and the like but will not increase with buildup of frost and on the contrary, will decrease with buildup of frost. By comparing the airflow velocity in both bypass ducts a defrost signal can be obtained that will accurately correspond to the given amount of frost buildup on the coil irrespective of the randomness of the frost buildup or of changes in blower speed or the like. In the preferred form of this invention, the airflow velocity sensor in each bypass duct is an air-cooled electrical resistor connected in a resistance bridge circuit. In order to maximize the sensitivity of the air-cooled sensing resistors in the system, the range of air velocities through the bypass ducts may be adjusted by throttle valves if desired.
Other advantages and features of the invention will be apparent with reference to the following specification and drawings.
BRIEF DESCRIPTION OF THE DRAWINGS FlG. l is a sectional elevation of an air-cooled refrigeration system having the frost detecting arrangement of the invention; and
FIG. 2 is a schematic of the bridge circuit of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 of the drawings, the evaporator coil lltl is shown to be positioned within a main airflow duct 11 having a blower fan 12 in the inlet side thereof and a constructed outlet side 13. A first bypass duct 15 is connected to the main duct 11 on each side of the evaporator coil as shown at 16 and 17 respectively. An airflow velocity sensing device lltl is located within the first bypass duct 15 and a throttle valve 19 may be provided to control the range of air velocities through the bypass duct 15 if desired. A second bypass duct 20 which is a reference bypass duct is connected across the constriction in the outlet side of the main duct lllr It will be noted that the constriction for the main duct 11 is formed by the converging duct wall 25 to which one end 26 of the reference bypass duct 20 is connected. The other end 27 of the reference bypass duct 20 is connected to the constricted outlet side 12 of the main duct 11. An airflow velocity sensing device 23 is located within the reference bypass duct 20 and if desired a throttling valve 24 may also be provided to control the range of airflow velocities passing through the reference bypass duct 20.
For a given speed of the blower fan 12, the airflow velocity in the first bypass duct l5 will increase when frost builds up on the evaporator coil It) to impede or block the flow of air from the blower 112 through the main duct 11. Of course any change in the main flow velocity due to a change in blower fan speed 12 will also change the flow velocity in the first bypass duct 15. Therefore if the flow-rate sensor 18 is calibrated to provide a signal for a particular flow velocity, a false defrost signal could be obtained when the flow velocity increases in the bypass duct 15 due to an increase in speed for the blower fan 12. To compensate for any change in the main flow rate as provided by the speed of the blower 12, a reference bypass duct 20 is mounted across the constriction in the outlet 13 of the main airflow duct 11. The static pressure drop across the constriction varies approximately as the square law of the total mass airflow velocity, as it does across a well-known Venturi flow meter. The reference duct flow velocity, being a square root law of the static pressure drop, will therefore be proportional to the total mass flow velocity. By comparing the two signals from the airflow velocity sensors 18 and 23 in the bypass ducts 1S and 20, respectively, a defrost signal can be obtained which will indicate or detect the buildup of frost on the evaporator coil 10 regardless of changes in main airflow provided by the blower fan 12 and regardless of the randomness ofthe frost buildup on the coil 10.
Although the invention in its broadest sense is not limited to a particular type of airflow velocity sensor to be used in the bypass ducts 15 and 20, the preferred form of the invention employs air-cooled temperature sensitive resistors in a re sistance bridge circuit.
Referring to FIG. 2 of the drawing, the airflow temperature sensitive resistor 18 in the first bypass duct 15 is connected in a resistance bridge circuit with the adjustable resistor 30, fixed resistor 31 and the airflow sensing temperature sensitive resistor 23 in the reference bypass duct 20. Each of the temperature sensitive resistors 18 and 23 may preferably have a posi tive temperature coefficient although the invention is not limited to the use of such resistors since it would be obvious to anyone skilled in the art that other forms of temperature sensitive resistors such as those having; negative temperature characteristics may also be used. A direct current power supply 33 is connected to the input terminals of the resistance bridge circuit and a defrost signal can be obtained by an unbalance of the bridge across the output terminals 34 and 25. The adjustable resistor 30 is adjusted to balance the bridge for no output signal when the airflow rates sensed by the sensing resistors 18 and 23 are of the order corresponding to a condition of less than the undesired amount of frost on the evaporator coil 10. When the frost has built up on the evaporator coil 10 to an undesired amount the increase in flow velocity through the first bypass duct 15 relative to the flow velocity sensed by the reference bypass duct 20 would change the resistance of the sensing resistor 18 relative to the sensing resistor 23 such as to unbalance the bridge and provide a defrost initiation signal across the bridge output terminals 34 and 35. it is known that some temperature sensing resistors would have different sensitivities for different velocities of airflow across the resistors to cool the same. In order to maximize the sensitivity of the flow-rate temperature sensing resistors 18 and 23, the throttle valves 19 and 24 may be provided in the respective bypass ducts l5 and 20. It should now be obvious to anyone skilled in the art that by suitably adjusting the throttle valves 19 and 24 and by suitably adjusting the bridge balancing resistor 30 a desired sensitivity and range of operation for the frost detector of the invention will be obtained.
It will be noted that each of the bypass ducts l5 and have cross-sectional areas considerably less than the cross-sectional area of the main duct 11 including the cross-sectional area of the constricted outlet 13 of the main duct 11. This is of course desirable in order to prevent either bypass duct from effectively shunting the evaporator coil or the system and is also desirable in improving the sensitivity of the system. There has been no description of the apparatus for utilizing the defrost signal generated across the bridge output terminals 34, 35 since any well-known defrosting apparatus may be used and such apparatus is not a part of the present invention. Although the reference bypass duct 20 is shown to have one end 21 connected along the converging constriction wall 25 of the duct 11, it should be understood that the end 21 of the reference bypass duct 20 may be connected at any point along the main duct 11 upstream from the constricted outlet 13.
Various modifications will occur to those skilled in the art.
I claim:
1. A frost detector for an air-cooling refrigeration system comprising, a main airflow duct, an evaporator coil substantially enclosed in said duct, means to force air to be cooled through said duct and coil from an inlet side to an outlet side of the duct, the outlet side of said duct having a constriction to reduce the cross-sectional area of the duct, a first bypass airflow conduit connected to said duct on each side of said coil ahead of the constriction of the duct, a second bypass reference airflow conduit connected to the outlet side of said duct between spaced points along the constriction of the duct, said first and second bypass conduits having cross-sectional areas considerably less than any cross-sectional areas of the duct, a respective airflow velocity sensor in each of said first and second bypass conduits, and means to compare the airflow velocity sensed by each sensor in the respective bypass conduits so that a change in airflow velocity through said coil due to the accumulation of frost on said coil may be detected regardless of variations in operation of the means to force air through the duct and coil and the randomness of the accumulation of frost on the coil.
2. The invention of claim 1 in which each sensor is comprised of an air-cooled electrical resistor, and each sensor resistor is connected in a resistance bridge circuit to compare their changes in resistance due to changes in airflow through the respective bypass flow sensing conduits.
3. The invention of claim 1 in which each of said bypass conduits is provided with a variably controlled airflow throttle to facilitate the comparison of sensed changes in airflow through the respective bypass conduits.
4. The invention of claim 3 in which each sensor is comprised of an air-cooled electrical resistor, and each sensor resistor is connected in a resistance bridge circuit to compare their changes in resistance due to changes in airflow velocities through the respective bypass conduits.

Claims (4)

1. A frost detector for an air-cooling refrigeration system comprising, a main airflow duct, an evaporator coil substantially enclosed in said duct, means to force air to be cooled through said duct and coil from an inlet side to an outlet side of the duct, the outlet side of said duct having a constriction to reduce the cross-sectional area of the duct, a first bypass airflow conduit connected to said duct on each side of said coil ahead of the constriction of the duct, a second bypass reference airflow conduit connected to the outlet side of said duct between spaced points along the constriction of the duct, said first and second bypass conduits having cross-sectional areas considerably less than any cross-sectional areas of the duct, a respective airflow velocity sensor in each of said first and second Bypass conduits, and means to compare the airflow velocity sensed by each sensor in the respective bypass conduits so that a change in airflow velocity through said coil due to the accumulation of frost on said coil may be detected regardless of variations in operation of the means to force air through the duct and coil and the randomness of the accumulation of frost on the coil.
2. The invention of claim 1 in which each sensor is comprised of an air-cooled electrical resistor, and each sensor resistor is connected in a resistance bridge circuit to compare their changes in resistance due to changes in airflow through the respective bypass flow sensing conduits.
3. The invention of claim 1 in which each of said bypass conduits is provided with a variably controlled airflow throttle to facilitate the comparison of sensed changes in airflow through the respective bypass conduits.
4. The invention of claim 3 in which each sensor is comprised of an air-cooled electrical resistor, and each sensor resistor is connected in a resistance bridge circuit to compare their changes in resistance due to changes in airflow velocities through the respective bypass conduits.
US91299A 1970-11-20 1970-11-20 Frost detector for refrigeration system Expired - Lifetime US3643457A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US9129970A 1970-11-20 1970-11-20

Publications (1)

Publication Number Publication Date
US3643457A true US3643457A (en) 1972-02-22

Family

ID=22227070

Family Applications (1)

Application Number Title Priority Date Filing Date
US91299A Expired - Lifetime US3643457A (en) 1970-11-20 1970-11-20 Frost detector for refrigeration system

Country Status (3)

Country Link
US (1) US3643457A (en)
JP (1) JPS4946811B1 (en)
CA (1) CA950555A (en)

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3726104A (en) * 1971-02-12 1973-04-10 Thermo King Corp Refrigeration system defrost initiation apparatus
US3826103A (en) * 1972-08-07 1974-07-30 P Grover Appliance defrosting system and switch means
US4007603A (en) * 1974-05-10 1977-02-15 Projectus Industriprodukter Ab Apparatus for defrosting of an evaporator in a heat pump
FR2376379A1 (en) * 1977-01-03 1978-07-28 Electric Power Res Inst HEAT PUMP DEFROST DEVICE
US4191026A (en) * 1977-02-14 1980-03-04 Electric Power Research Institute, Inc. Apparatus for defrosting low temperature heat exchanger
US5669813A (en) * 1996-05-03 1997-09-23 Ford Motor Company Apparatus for storing and cooling electronic devices and/or modules in a vehicle
US20070012052A1 (en) * 2005-02-23 2007-01-18 Emerson Electric Co. Interactive control system for an HVAC system
US20140150477A1 (en) * 2012-11-30 2014-06-05 Yi Qu Defrost Control Using Fan Data
WO2019166291A1 (en) * 2018-02-28 2019-09-06 BSH Hausgeräte GmbH Refrigeration appliance comprising a defrost heater
CN111801539A (en) * 2018-03-08 2020-10-20 Lg电子株式会社 Refrigerator and control method thereof
CN111868462A (en) * 2018-03-26 2020-10-30 Lg电子株式会社 Refrigerator and control method thereof
CN111886462A (en) * 2018-03-26 2020-11-03 Lg电子株式会社 Refrigerator and control method thereof

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5134818U (en) * 1974-09-06 1976-03-15
JPS61128080U (en) * 1985-01-31 1986-08-11
JPH0717576U (en) * 1993-09-07 1995-03-28 株式会社野口紙工 Binding device

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3039278A (en) * 1959-01-02 1962-06-19 Parnall & Sons Ltd Means for de-frosting refrigerating apparatus
US3355904A (en) * 1966-01-21 1967-12-05 Texas Instruments Inc Differential fluid velocity sensing
US3362183A (en) * 1966-01-21 1968-01-09 Texas Instruments Inc Fluid flow control in refrigeration systems
US3377817A (en) * 1966-12-27 1968-04-16 Trane Co Defrost control for heating and cooling refrigeration systems
US3465534A (en) * 1967-10-31 1969-09-09 Texas Instruments Inc Differential flow sensing apparatus
US3487654A (en) * 1968-05-14 1970-01-06 Ranco Inc Deicing control apparatus for forced air refrigeration system

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3039278A (en) * 1959-01-02 1962-06-19 Parnall & Sons Ltd Means for de-frosting refrigerating apparatus
US3355904A (en) * 1966-01-21 1967-12-05 Texas Instruments Inc Differential fluid velocity sensing
US3362183A (en) * 1966-01-21 1968-01-09 Texas Instruments Inc Fluid flow control in refrigeration systems
US3377817A (en) * 1966-12-27 1968-04-16 Trane Co Defrost control for heating and cooling refrigeration systems
US3465534A (en) * 1967-10-31 1969-09-09 Texas Instruments Inc Differential flow sensing apparatus
US3487654A (en) * 1968-05-14 1970-01-06 Ranco Inc Deicing control apparatus for forced air refrigeration system

Cited By (22)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3726104A (en) * 1971-02-12 1973-04-10 Thermo King Corp Refrigeration system defrost initiation apparatus
US3826103A (en) * 1972-08-07 1974-07-30 P Grover Appliance defrosting system and switch means
US4007603A (en) * 1974-05-10 1977-02-15 Projectus Industriprodukter Ab Apparatus for defrosting of an evaporator in a heat pump
FR2376379A1 (en) * 1977-01-03 1978-07-28 Electric Power Res Inst HEAT PUMP DEFROST DEVICE
US4191026A (en) * 1977-02-14 1980-03-04 Electric Power Research Institute, Inc. Apparatus for defrosting low temperature heat exchanger
US5669813A (en) * 1996-05-03 1997-09-23 Ford Motor Company Apparatus for storing and cooling electronic devices and/or modules in a vehicle
US20070012052A1 (en) * 2005-02-23 2007-01-18 Emerson Electric Co. Interactive control system for an HVAC system
US8550368B2 (en) * 2005-02-23 2013-10-08 Emerson Electric Co. Interactive control system for an HVAC system
US20140150477A1 (en) * 2012-11-30 2014-06-05 Yi Qu Defrost Control Using Fan Data
US9341405B2 (en) * 2012-11-30 2016-05-17 Lennox Industries Inc. Defrost control using fan data
US10352611B2 (en) 2012-11-30 2019-07-16 Lennox Industries Inc. Defrost control using fan data
WO2019166291A1 (en) * 2018-02-28 2019-09-06 BSH Hausgeräte GmbH Refrigeration appliance comprising a defrost heater
CN111801539A (en) * 2018-03-08 2020-10-20 Lg电子株式会社 Refrigerator and control method thereof
CN111868462A (en) * 2018-03-26 2020-10-30 Lg电子株式会社 Refrigerator and control method thereof
CN111886462A (en) * 2018-03-26 2020-11-03 Lg电子株式会社 Refrigerator and control method thereof
CN111868462B (en) * 2018-03-26 2022-04-15 Lg电子株式会社 Refrigerator and control method thereof
CN111886462B (en) * 2018-03-26 2022-05-03 Lg电子株式会社 Refrigerator and control method thereof
CN114704993A (en) * 2018-03-26 2022-07-05 Lg电子株式会社 Control method of refrigerator
CN114777395A (en) * 2018-03-26 2022-07-22 Lg电子株式会社 Control method of refrigerator
CN114777395B (en) * 2018-03-26 2023-11-03 Lg电子株式会社 Control method of refrigerator
US11867448B2 (en) 2018-03-26 2024-01-09 Lg Electronics Inc. Refrigerator and method for controlling the same
CN114704993B (en) * 2018-03-26 2024-04-02 Lg电子株式会社 Control method of refrigerator

Also Published As

Publication number Publication date
JPS4946811B1 (en) 1974-12-12
CA950555A (en) 1974-07-02

Similar Documents

Publication Publication Date Title
US3643457A (en) Frost detector for refrigeration system
US3795145A (en) Variable throat venturi airspeed sensor
US4083244A (en) Method and apparatus for measuring fluid flow and/or for exercising a control in dependence thereon
US7174791B2 (en) Method and device for measuring airflows through HVAC grilles
US4343194A (en) Flow sensing apparatus
US4213335A (en) Flow rate meter with temperature dependent resistor
US2726546A (en) Apparatus for measuring fluid flow
US4248055A (en) Hot gas bypass control for centrifugal liquid chillers
US4283944A (en) Apparatus for measuring the mass of a fluid medium
US4154088A (en) Apparatus for measuring the particulate matter content of a gas
JPH0671124A (en) Device for detecting blockage of air filter
US4254659A (en) Fluid dynamic angular rate sensor
US2603422A (en) Temperature control system
GB2040471A (en) Device for measuring the mass flow of a flowing medium
US5209113A (en) Air flow meter
GB2157447A (en) Heat exchange equipment
US4372170A (en) Flow measuring apparatus
JPH0317284B2 (en)
GB1159171A (en) Differential Fluid Velocity Sensing
US4596140A (en) Constant overheat anemometer with sensor lead wire impedance compensation
US2624199A (en) Fluid flowmeter
US4052897A (en) Methods and apparatus for determining total flow rate of gaseous fluids
JPS61217641A (en) Ventilating facility for controlling absolute interior pressure
JPH0682282A (en) Measuring equipment for flow rate
JPH10320057A (en) Flow rate control valve device