Defrosting method and apparatus

Claim 3

A method of defrosting, as claimed in claim 1, including continuing the defrosting until the ratio of the detected temperature difference to the maximum temperature difference re-attains the preset value; and then terminating the defrosting.

Claim 4

A method of defrosting, as claimed in claim 2, including the step of, when the ratio of the detected temperature difference to the maximum temperature difference decreases below such preset value to another and lower preset value, initiating forced heating of the first heat exchanger.

Claim 5

Apparatus for controlling defrosting of a first heat exchanger, on the heat source side of refrigerating apparatus, having a second heat exchanger, on the utilization side, and a fluid flow circuit interconnecting said two heat exchangers, comprising, in combination, respective temperature sensing means detecting the temperature of the fluid entering said second heat exchanger and detecting the temperature of the fluid leaving said second heat exchanger; first means operable by said temperature sensing means to determine and store the maximum temperature difference between the inlet fluid temperature and the outlet fluid temperature of said second heat exchanger; second means operable by said temperature sensing means, during operation of the refrigerating apparatus, in accordance with the difference between the inlet and outlet fluid temperatures of said second heat exchanger; and third means operable conjointly by said first and second means, when the ratio of the detected temperature difference to the maximum temperature difference decreases below a preset value, due to icing of said first hEat exchanger, to iniitiate a defrosting cycle of said first heat exchanger.

Claim 6

Apparatus for controlling defrosting of a first heat exchanger, on the heat source side of refrigerating apparatus, having a second heat exchanger, on the utilization side, and a fluid flow circuit interconnecting said two heat exchangers, comprising, in combination, respective temperature sensing means detecting the temperature of the fluid entering said second heat exchanger and detecting the temperature of the fluid leaving said second heat exchanger; first means operable by said temperature sensing means to determine and store the maximum temperature difference between the inlet fluid temperature and the outlet fluid temperature of said second heat exchanger; second means operable by said temperature sensing means, during operation of the refrigerating apparatus, in accordance with the difference between the inlet and outlet fluid temperatures of said second heat exchanger; and third means operable conjointly by said first and second means, when the ratio of the detected temperature difference to the maximum temperature difference decreases below a preset value, due to icing of said first hEat exchanger, to iniitiate a defrosting cycle of said first heat exchanger.

Claim 7

Apparatus, as claimed in claim 4, in which said first and second means conjointly operate said third means to terminate defrosting responsive to the ratio of the detected temperature difference to the maximum temperature difference re-attaining said preset value.

Claim 8

Apparatus, as claimed in claim 4, including fourth means operable by said second means when the ratio of the detected temperature difference to the maximum temperature difference attains a predetermined value which is below said preset value, to initiate forced heating of said first heat exchanger.

Claim 9

Apparatus for controlling defrosting of a first heat exchanger, on the heat source side of refrigerating apparatus, having a second heat exchanger, on the utilization side, and a fluid flow circuit interconnecting said two heat exchangers, comprising, in combination, respective temperature sensing means detecting the temperature of the fluid entering said second heat exchanger and detecting the temperature of the fluid leaving said second heat exchanger; first means operable by said temperature sensing means to determine and store the maximum temperature difference between the inlet fluid temperature and the outlet fluid temperature of said second heat exchanger; second means operable by said temperature sensing means, during operation of the refrigerating apparatus, in accordance with the difference between the inlet and outlet fluid temperatures of said second heat exchanger; and third means operable conjointly by said first and second means, when the ratio of the detected temperature difference to the maximum temperature difference decreases below a preset value, due to icing of said first heat exchanger, to initiate a defrosting cycle of said first heat exchanger; said second means comprising a first lever pivoted intermediate its ends and subjected to both said temperature sensing means operating on an end of said lever in opposition to each other; said first means comprising a second lever in opposition to each other; said first means comprising a second lever pivoted coaxially with said first lever and movable by said first lever in a direction corresponding to the maximum temperature difference between the inlet fluid temperature and the outlet fluid temperature of said second heat exchanger; said second lever having a pointed free end; and a spring biased finely serrated member engageable with the pointed end of said second lever and operable to retain said second lever at a position corresponding to the maximum temperature difference between the inlet fluid temperature and the outlet fluid temperature of said second heat exchanger; said first lever being movable away from said second lever by said temperature sensing means responsive to a decreaese in the temperature difference between the inlet fluid temperature and the outlet fluid temperature of said second heat exchanger.

Claim 10

Apparatus for controlling defrosting of a first heat exchanger, on the heat source side of refrigerating apparatus, having a second heat exchanger, on the utilization side, and a fluid flow circuit interconnecting said two heat exchangers, comprising, in combination, respective temperature sensing means detecting the temperature of the fluid entering said second heat exchanger and detecting the temperature of the fluid leaving said second heat exchanger; first means operable by said temperature sensing means to determine and store the maximum temperature difference between the inlet fluid temperature and the outlet fluid temperature of said second heat exchanger; second means operable by said temperature sensing means, during operation of the refrigerating apparatus, in accordance with the difference between the inlet and outlet fluid temperatures of said second heat exchanger; and third means operable conjointly by said first and second means, when the ratio of the detected temperature difference to the maximum temperature difference decreases below a preset value, due to icing of said first heat exchanger, to initiate a defrosting cycle of said first heat exchanger; said second means comprising a first lever pivoted intermediate its ends and subjected to both said temperature sensing means operating on an end of said lever in opposition to each other; said first means comprising a second lever in opposition to each other; said first means comprising a second lever pivoted coaxially with said first lever and movable by said first lever in a direction corresponding to the maximum temperature difference between the inlet fluid temperature and the outlet fluid temperature of said second heat exchanger; said second lever having a pointed free end; and a spring biased finely serrated member engageable with the pointed end of said second lever and operable to retain said second lever at a position corresponding to the maximum temperature difference between the inlet fluid temperature and the outlet fluid temperature of said second heat exchanger; said first lever being movable away from said second lever by said temperature sensing means responsive to a decreaese in the temperature difference between the inlet fluid temperature and the outlet fluid temperature of said second heat exchanger.

Claim 11

Apparatus, as claimed in claim 7, including a first adjustable resistor operable by said first lever; a second adjustable resistor operable by said second lever; and a source of potential; said third means comprising a bridge circuit connected to said source of potential and including said first and second adjustable resistors and a pair of fixed resistors, said bridge further including a relay connected between a pair of junctions thereof.

Claim 12

Apparatus, as claimed in claim 7, in which said third means comprises a switch carried by one of said levers and having an operator, and an adjustable abutment carried by the other of said levers and engageable with said operator to operate said switch responsive to a predetermined displacement of said first lever in a direction away from said second lever; said switch, when operated, initiating a defrosting cycle of said first heat exchanger.

Claim 13

Apparatus, as claimed in claim 9, including a second switch having a second operator; and a second abutment on said first lever; said second abutment engaginG said operator to operate said second switch responsive to the ratio of the detected temperature difference to the maximum temperature difference decreasing to a second predetermined value below said preset value; said second switch, when operating, initiating forced heating of said first heat exchanger.