Sensor for coil defrost in a refrigeration system evaporator

Patent metadata

Field	Value
Publication number	US-2016018154-A1
Application number	US-201514705781-A
Country	US
Kind code	A1
Filing date	May 6, 2015
Priority date	May 6, 2014
Publication date	Jan 21, 2016
Grant date	—

Abstract

A system for controlling the defrost cycle of an evaporator comprising a sensor in the coil of an evaporator or downstream of the coil, the sensor configured to determine changes in the liquid mass ratio of the refrigerant in the evaporator. The difference in liquid mass ratio relating to frost buildup on the outside of said evaporator. When the difference in liquid mass ratio reaches a predetermined amount, corresponding to an unsatisfactory frost buildup, a defrost cycle is initiated. When the liquid mass ratio returns to a value that corresponds to a defrosted evaporator, the defrost cycle is discontinued.

First claim

1 . A method for controlling the defrost cycle of an evaporator, comprising:
detecting a first ratio of liquid refrigerant to refrigerant in a vapor phase at a location in said evaporator or downstream of said evaporator by detecting a first capacitance between two electrodes; detecting a second ratio of liquid refrigerant to refrigerant in a vapor phase at said location at a different time by detecting a second capacitance between said two electrodes; initiating a defrost cycle for said evaporator when a difference between said first capacitance and said second capacitance equals or exceeds a predetermined amount; wherein said two electrodes comprise a first electrode comprising a metal portion of a pipe through which said refrigerant is flowing and a second electrode comprising an array of metal rods arranged parallel to one-another inside said pipe, and electrically connected to one-another, but not touching one-another, and not touching the inside surface of the pipe, and wherein the distance between the metal rods and the inside surface of the pipe is sufficient to allow refrigerant to freely flow between said rods and the inside surface of the pipe.

2 . A method according to claim 1 , further comprising detecting a third ratio of liquid refrigerant to refrigerant at said location, and stopping a defrost cycle for said evaporator when said third ratio is the same or within a predetermined amount of said first ratio.

3 . A method according to claim 1 , wherein said first ratio is determined when said evaporator has no frost.

4 . A method according to claim 1 , wherein said difference between said first ratio and said second ratio corresponds to a difference in volumes of liquid passing said location.

5 . A method according to claim 1 , wherein said difference between said first capacitance and said second capacitance corresponds to a difference in volumes of liquid passing between said charged plates.

6 . A method according to claim 1 , wherein said predetermined amount may be changed according to operator preference.

7 . An evaporating refrigerant cooling system comprising an evaporator coil, a liquid mass ratio sensor located in said coil or downstream of said coil, and a control system configured to initiate a coil defrost cycle when said liquid mass ratio sensor outputs a value that equals or exceeds a predetermined value and to discontinue said defrost cycle when said liquid mass ratio sensor outputs a second value that is equal to or less than a second predetermined value, said liquid mass ratio sensor comprising spaced-apart conductive elements configured to receive a charge, said sensor configured to take capacitance readings reflective of a volume of fluid passing between said plates;
wherein said spaced-apart conductive elements comprise a first electrode comprising a metal portion of a pipe through which said refrigerant is flowing and a second electrode comprising an array of metal rods arranged parallel to one-another inside said pipe, and electrically connected to one-another, but not touching one-another, and not touching the inside surface of the pipe, and wherein the distance between the metal rods and the inside surface of the pipe is sufficient to allow refrigerant to freely flow between said rods and the inside surface of the pipe.

8 . An apparatus according to claim 7 , wherein said metal rods are arranged in an arc, where each metal rod is configured to be the same distance from the inside surface of the pipe.

9 . An apparatus according to claim 7 , wherein said metal rods are arranged in a plane across an interior of said pipe.

10 . An apparatus according to claim 7 , wherein said metal rods are supported between two supports, each support defining a plurality of recesses in a rod-facing surface, said recesses configured to receive and support said rods and to keep them separated from one-another.

11 . A liquid mass ratio sensor comprising spaced-apart conductive elements configured to receive a charge, said sensor configured to take capacitance readings reflective of a volume of fluid passing between said conductive elements;
wherein said spaced-apart conductive elements comprise a first electrode comprising a metal portion of a pipe through which said refrigerant is flowing and a second electrode comprising an array of metal rods arranged parallel to one-another inside said pipe, and electrically connected to one-another, but not touching one-another, and not touching the inside surface of the pipe, and wherein the distance between the metal rods and the inside surface of the pipe is sufficient to allow refrigerant to freely flow between said rods and the inside surface of the pipe.

12 . An apparatus according to claim 11 , wherein said metal rods are arranged in an arc, where each metal rod is configured to be the same distance from the inside surface of the pipe.

13 . An apparatus according to claim 11 , wherein said metal rods are arranged in a plane across an interior of said pipe.

14 . An apparatus according to claim 11 , wherein said metal rods are supported between two supports, each support defining a plurality of recesses in a rod-facing surface, said recesses configured to receive and support said rods and to keep them separated from one-another.

15 . An electrode configured for use in a liquid mass ratio sensor, said electrode comprising: an array of metal rods arranged parallel to one-another and electrically connected to one-another, but not touching one-another, wherein the distance between the metal rods and the is sufficient to allow refrigerant to freely flow between said.

16 . An electrode according to claim 15 , wherein said metal rods are arranged in an arc.

17 . An electrode according to claim 15 , wherein said metal rods are arranged in a.

18 . An electrode according to claim 15 , wherein said metal rods are supported between two supports, each support defining a plurality of recesses in a rod-facing surface, said recesses configured to receive and support said rods and to keep them separated from one-another.

Assignees

• Evapco Inc

Inventors

• Derosier Greg

Classifications

• G01N27/226

  Construction of measuring vessels; Electrodes therefor · CPC title

• F25D21/02 Primary

  Detecting the presence of frost or condensate · CPC title

• F25B2700/11

  Sensor to detect if defrost is necessary · CPC title

• F25D21/006

  with electronic control circuits · CPC title

• F25D21/06

  Removing frost (defrosting cycles F25B47/02) · CPC title