WO1996022493A1

WO1996022493A1 - Refrigeration system early alarm

Info

Publication number: WO1996022493A1
Application number: PCT/US1995/016974
Authority: WO
Inventors: Avraham Cohen
Original assignee: Ben-Dov, Uri; Ben-Dov, Dan; Ben-Dov, Dov; Friedman, Mark, M.
Priority date: 1995-01-20
Filing date: 1995-12-29
Publication date: 1996-07-25
Also published as: IL112405A0; AU4743396A; IL112405A

Abstract

A refrigeration system monitoring and alarm system for alerting of a reduction in refrigerant level. The system includes a refrigerant monitoring vessel (10) having a refrigerant inlet (12) and a refrigerant outlet (14), the vessel being full of refrigerant during normal operations. The system also includes a refrigerant inlet line (16) connected to the refrigerant inlet, a refrigerant outlet line (18) connected to the refrigerant outlet and a sensor (20) for continually sensing a property related to the actual level of refrigerant in the refrigerant monitoring vessel. The sensor produces electrical signals related to the actual level of refrigerant. The system further includes a processor (22) which is electrically connected to the sensor (20) for receiving the signals and for determining the adequacy of the refrigerant level in the refrigerant monitoring vessel and an alarm output mechanism (24) for providing alarms (50, 52, 54) related to the level of the refrigerant in the refrigerant monitoring vessel.

Description

REFRIGERATION SYSTEM EARLY ALARM

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to refrigeration systems and, more

particularly, to a alarms designed to warn of malfunctions in the

refrigeration system.

Refrigeration systems are in use in various applications. Certain of

these applications are domestic, such as domestic refrigeration and air-

conditioning. Refrigeration systems are also used in various industrial or

commercial, for example, in the refrigeration of large compartments which

house perishable foods, and the like.

A typical refrigeration system includes a closed refrigeration loop

through which flows a refrigerant, such as Freon, for example. The

refrigerant, through continual vaporization and liquefaction, is used to

remove heat from the refrigerated compartment. Thus, liquid refrigerant

is made to pass through heat exchanger tubes nning through the

compartment to be cooled. Heat from the compartment vaporizes the

refrigerant which now becomes gaseous. The gaseous refrigerant is

liquefied using a compressor with the release of heat to the atmosphere and

the liquid refringent is recycled back to the compartment to be cooled to

pick up additional heat. The ultimate purpose of the refrigeration system is to maintain a

certain maximum temperature in the compartment or space being

refrigerated. The actual temperature may vary depending on

circumstances. For example, the temperature could increase undesirably

because of the addition of a large amount of relatively warm merchandise

into the space or because a door to a warmer atmosphere is left open for

a sufficiently long period. Furthermore, the temperature could rise due to

a malfunction of the refrigeration system, most commonly a leakage and

loss of refrigerant.

To avoid the possible loss and inconvenience due to temperatures

which rise above the acceptable levels, it is very common, especially in

commercial or industrial refrigeration systems, to monitor the temperature

of the space or compartment being cooled. Thus, when an unacceptably

high temperature is detected by the temperature sensor a suitable alarm is

issued so as to bring the problem to the attention of the proper personnel

so that corrective measures may be taken.

Unfortunately, such systems suffer from a basic difficulty in that the

warning is typically issued too late to avoid potentially very large losses.

To understand why this is the case one must remember that an efficient

alarm system must have a certain degree of insensitivity so that small

perturbations in the temperature of the space do not automatically set off

a false alarm. For example, if the desired temperature is -20 °C it may happen that if the compartment door is left open for five rninutes the

temperature at the sensor will rise to -18 °C. If the alarm setpoint is -19°C

then an alarm will issue which should not have been. Thus, to avoid an

inordinate amount of false alarms, the setpoint is often fixed at a

substantially higher temperature level, say, -5°C.

Unfortunately, the activation of an alarm at such high setpoints

gives little time for repair, so that in the case of a refrigeration system

failure there is insufficient time to bring in repairmen and complete the

necessary repairs before the temperature rises sufficiently beyond the

setpoint temperature to result in damage or loss of the merchandise being

cooled.

There is thus a widely recognized need for, and it would be highly

advantageous to have, a way of continually monitoring a refrigeration

system so as to detect, and alert of, system malfunctions before the

malfunction has resulted in a rise of the temperature of the compartment

or space being cooled in order to provide sufficient time to correct the

malfunction before damage is incurred to the contents of the refrigerated

compartment or space.

SUMMARY OF THE INVENTION

According to the present invention there is provided a refrigeration

system monitoring and alarm system for alerting of a reduction in refrigerant level, comprising: (a) a refrigerant monitoring vessel having a

refrigerant inlet and a refrigerant outlet, the vessel being full of refrigerant

during normal operations; (b) a refrigerant inlet line connected to the

refrigerant inlet; (c) a refrigerant outlet line connected to the refrigerant

outlet; (d) a sensor for continually sensing a property related to the actual

level of refrigerant in the refrigerant monitoring vessel, the sensor

producing electrical signal related to the actual level of refrigerant; (e) a

processor electrically connected to the sensor for receiving the signals and

for determining the adequacy of the refrigerant level in the refrigerant

monitoring vessel; (f) an alarm output mechanism for providing alarms

related to the level of the refrigerant in the refrigerant monitoring vessel.

According to further features in preferred embodiments of the

invention described below, the alarm output mechanism is activated with

a delay following the receipt of the signals indicating an inadequate

refrigerant level, preferably only after the signals indicative of an

inadequate refrigerant level have been sensed for a preset minimum time.

According to still further features in the described preferred

embodiments the sensor operates by detecting the reflection of

electromagnetic radiation from the top surface of the refrigerant in the

refrigerant monitoring vessel.

The present invention successfully addresses the shortcomings of the

presently known configurations by providing a simple and reliable system for providing advance warning of malfunctions in a refrigeration system

while there is still adequate time to effect the necessary repairs.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, with

reference to the accompanying drawings, wherein:

FIG. 1 is a plan view of the contents of a control box housing one

version of a system according to the present invention;

FIG. 2 is a side view of the outside of the control box of Figure 1 ;

FIG. 3 is a front view of the outside of the control box of Figure

1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is of a system for a monitor and alarm system

for a refrigeration system which alerts of a reduction in refrigerant level.

The principles and operation of a system according to the present

invention may be better understood with reference to the drawings and the

accompanying description.

Referring now to the drawings, Figure 1 illustrates the contents of

a control box containing a monitor and alert system according to a typical

embodiment of the present invention. The monitoring and alarm system includes a refrigerant monitoring

vessel 10, typically made of metal and sufficiently rugged to safely

withstand the pressures found in the liquid refrigerant portion of the

refrigeration system. Vessel 10 has a refrigerant inlet opening 12 and

refrigerant outlet opening 14.

Refrigerant inlet opening 12 is connected to a refrigerant inlet line

16. Refrigerant outlet opening 14 is connected to a refrigerant outlet line

18. Thus, at least a portion and, preferably, all, of the liquid refrigerant

of the refrigeration system is made to pass through vessel 10.

Vessel 10 remains full of liquid refrigerant during normal

operations, i.e., when there is adequate amount of refrigerant in the

system and no losses. To ensure that any gas bubbles which might be

present in the system do not get trapped at the top of vessel 10, it is

optionally possible to have outlet line 18 leave from the top of vessel 10

or to add a gas escape pipe from the top of vessel 10 to allow any trapped

gas to escape vessel 10, thereby allowing the liquid level in vessel 10 to

rise to the top of vessel 10.

A system according to the present invention further includes a

sensor 20 which is capable of continually sensing a property which is

related to the actual level of refrigerant, whether absolute or relative, in

refrigerant monitoring vessel 10. Sensor 20 produces electrical signals

which are related to the actual level of refrigerant in vessel 10. Various indirect sensors may be used to detect the liquid level in

vessel 10. These include, but are not limited to, measurement of the

liquid hydrostatic head developed by the liquid, measurement of the

buoyant force created when a detecting member is partially or completely

immersed in the liquid.

Various direct sensors may be used to sense the liquid level. These

include, but are not limited to, the determination of the position of a

detecting member which rides on the liquid surface, such as a ball or other

type of float, the contact of electrode probes with the liquid surface, the

interruption of a light beam to a photoelectric cell, and the like.

Preferably, sensor 20 uses the reflection of electromagnetic waves, such

as radio or radar waves, or sonic waves to determine the location of the

upper surface of the liquid.

A system according to the present invention further includes a

processor 22 which is electrically connected to sensor 22 for receiving

signals related to the liquid which are produced by sensor 22 and for

determirύng the adequacy of the refrigerant level in refrigerant monitoring

vessel 10 according to preset criteria.

Finally, a system according to the present invention further includes

an alarm output mechanism 24 for providing alarms, initiated by processor

22 which are related to said level of refrigerant in refrigerant monitoring

vessel 10. Alarm output mechanism 24 may be any suitable mechanism,

including, but not limited to, any audible and/or visible alarms and/or

telephone communication.

Shown in Figure 2 is a loudspeaker 40 mounted on the housing of

a system according to the present invention for providing audible alarms.

Additionally or alternatively, audio leads 42 are provided for activating a

remote loudspeaker (not shown) located in some convenient location, such

as a control room or a location where personnel are more likely to hear

the alarm.

Similarly, shown in Figure 2 are telephone leads 44 for activating

a telephone so as to alert remotely located persons of a system

malfunction.

The alarm may be also or alternatively be given visible form, as by

the use of lights. Shown in Figure 2 are light leads 46 which activate

remotely located lights. Shown in Figure 3 is an illustrative example of

a set of lights located on the front panel. The three lights - green 50, blue

52 and red 54, can be used to provide visible information as to the level

of refrigerant in the refrigeration system. For example, whenever the

level is above the preset level, green light 50 is activated. Whenever the

level is below the present level, blue light 52 is activated in addition to,

or in place of, green light 50. Finally, when an alarm condition exits, as described below, red light 54 is activated, alerting personnel that

corrective steps are in order.

To avoid false alarms, the system preferably includes a certain

delay, typically executed by processor 22, before issuing an alarm. Thus,

for example, an alarm will not be issued immediately after the level of

liquid refrigerant drops below the preset level, but rather will be issued

after a preset time delay, and preferably only if the unacceptable low

refrigerant level has persisted for a certain period of time.

While the invention has been described with respect to a limited

number of embodiments, it will be appreciated that many variations,

modifications and other applications of the invention may be made.

Claims

WHAT IS CLAIMED IS:

1. A refrigeration system monitoring and alarm system for

alerting of a reduction in refrigerant level, comprising:

(a) a refrigerant monitoring vessel having a refrigerant inlet and

a refrigerant outlet, said vessel being full of refrigerant

during normal operations;

(b) a refrigerant inlet line connected to said refrigerant inlet;

(c) a refrigerant outlet line connected to said refrigerant outlet;

(d) a sensor for continually sensing a property related to the

actual level of refrigerant in said refrigerant monitoring

vessel, said sensor producing electrical signal related to said

actual level of refrigerant;

(e) a processor electrically connected to said sensor for receiving

said signals and for determining the adequacy of said

refrigerant level in said refrigerant monitoring vessel;

(f) an alarm output mechanism for providing alarms related to

said level of said refrigerant in said refrigerant monitoring

vessel.

2. A system as in claim 1 , wherein said alarm output

mechanism is activated with a delay following the receipt of said signals

indicating an inadequate refrigerant level.

3. A system as in claim 2, wherein said alarm output

mechanism is activated only after said signals indicative of an inadequate

refrigerant level have been sensed for a preset minimum time.

4. A system as in claim 1 , wherein said sensor operates by

detecting the reflection of electromagnetic radiation from the top surface

of the refrigerant in said refrigerant monitoring vessel.

5. A system as in claim 5, wherein said electromagnetic

radiation is radio waves.

6. A system as in claim 5, wherein said electromagnetic

radiation is radar waves.

7. A system as in claim 1 , wherein said sensor operates by

detecting the reflection of sonic waves from the top surface of the

refrigerant in said refrigerant monitoring vessel.

8. A system as in claim 1 , wherein said sensor includes a float

which rides on the top surface of the refrigerant in said refrigerant

monitoring vessel.

9. A system as in claim 1 , wherein said alarm output

mechanism includes an audible signal.

10. A system as in claim 9, wherein said audible signal is

produced at a location which is remote from said refrigerant monitoring

vessel.

11. A system as in claim 1 , wherein said alarm output

mechanism includes a visible signal.

12. A system as in claim 11 , wherein said visible signal is

produced at a location which is remote from said refrigerant monitoring

vessel.

13. A system as in claim 1, wherein said alarm output

mechanism includes a telephone line for activating a remote telephone

receiver.