ASHRAE Journal - August 2011 - 36

TEchnicAl FEATuRE

Liquid Refrigerant Pumping
In Industrial Refrigeration Systems

E

By Todd B. Jekel, Ph.D., P.E., Member ASHRAE, and Douglas T. Reindl, Ph.D., P.E., Fellow ASHRAE

arly practitioners of industrial refrigeration systems found they could increase the capacity of evaporators by supplying excess

liquid refrigerant to the unit (overfeeding). In evaporators configured to operate with overfeed, the quantity of liquid refrigerant supplied is greater than the minimum amount required to meet the cooling loads as it undergoes the phase change from liquid to vapor. In this case, a mixture of low temperature liquid and vapor leaves the evaporator and returns to a vessel designed to separate the liquid from the vapor prior to the vapor being recompressed.

Within limits, the cooling capacity of an overfed evaporator increases due to the tendency for more of the evaporator’s interior surfaces being wetted with saturated liquid refrigerant.1,2 Figure 1 shows a simple liquid overfed system typical of those designed and used today
36 ASHRAE Journal

for large built-up industrial refrigeration systems. In a mechanically pumped overfeed system, a centrifugal pump draws low temperature saturated liquid refrigerant from a vessel referred to as a “pumped recirculator,” “pumped acashrae.org

cumulator,” “recirculator,” or “lowpressure receiver” and raises the pressure of the liquid for delivery to one or more evaporators having a common refrigerant temperature requirement. Once pressurized by the pump, the saturated liquid becomes subcooled as it leaves the pump discharge and enters the “recirculated liquid supply line.” As individual evaporators call for cooling, local controls simply open a liquid feed solenoid valve, which allows low temperature pressurized liquid from the liquid supply line to flow into the evaporator. Manually adjustable hand-expansion (i.e., metering) valves are used at each evaporator as a means of balancing the supply of About the Authors
Todd B. Jekel, Ph.D., P.E., is assistant director and Douglas T. Reindl, Ph.D., P.E., is director of the Industrial Refrigeration Consortium and professor at the University of Wisconsin, Madison, Wis.

August 2011



ASHRAE Journal - August 2011

Table of Contents for the Digital Edition of ASHRAE Journal - August 2011

ASHRAE Journal - August 2011
Contents
Commentary
Industry News
Letters
Meetings and Shows
Feature Articles
2011–12 Presidential Address: Sustaining ASHRAE Through Leadership
Retrocommissioning Older Buildings
Liquid Refrigerant Pumping in Industrial Refrigeration Systems
Technology Award Case Studies:
Hospital Upgrade: Heat Recovery, Geothermal Save Energy
Cool Weather Savings: Using Hybrid Refrigeration Systems for Chiller Retrofit
Special Section
InfoCenter
Standing Columns
Solar NZEB Project
Emerging Technologies
Special Products
IAQ Applications
Washington Report
People
Products
Classified Advertising
Advertisers Index
ASHRAE Journal - August 2011 - Intro
ASHRAE Journal - August 2011 - ASHRAE Journal - August 2011
ASHRAE Journal - August 2011 - Cover2
ASHRAE Journal - August 2011 - 1
ASHRAE Journal - August 2011 - 2
ASHRAE Journal - August 2011 - Contents
ASHRAE Journal - August 2011 - Commentary
ASHRAE Journal - August 2011 - 5
ASHRAE Journal - August 2011 - Industry News
ASHRAE Journal - August 2011 - 7
ASHRAE Journal - August 2011 - 8
ASHRAE Journal - August 2011 - 9
ASHRAE Journal - August 2011 - Letters
ASHRAE Journal - August 2011 - 11
ASHRAE Journal - August 2011 - 12
ASHRAE Journal - August 2011 - 13
ASHRAE Journal - August 2011 - 14
ASHRAE Journal - August 2011 - 15
ASHRAE Journal - August 2011 - Meetings and Shows
ASHRAE Journal - August 2011 - 17
ASHRAE Journal - August 2011 - 2011–12 Presidential Address: Sustaining ASHRAE Through Leadership
ASHRAE Journal - August 2011 - 19
ASHRAE Journal - August 2011 - 20
ASHRAE Journal - August 2011 - 21
ASHRAE Journal - August 2011 - 22
ASHRAE Journal - August 2011 - 23
ASHRAE Journal - August 2011 - 24
ASHRAE Journal - August 2011 - 25
ASHRAE Journal - August 2011 - Retrocommissioning Older Buildings
ASHRAE Journal - August 2011 - 27
ASHRAE Journal - August 2011 - 28
ASHRAE Journal - August 2011 - 29
ASHRAE Journal - August 2011 - 30
ASHRAE Journal - August 2011 - 31
ASHRAE Journal - August 2011 - 32
ASHRAE Journal - August 2011 - 33
ASHRAE Journal - August 2011 - 34
ASHRAE Journal - August 2011 - 35
ASHRAE Journal - August 2011 - Liquid Refrigerant Pumping in Industrial Refrigeration Systems
ASHRAE Journal - August 2011 - 37
ASHRAE Journal - August 2011 - 38
ASHRAE Journal - August 2011 - 39
ASHRAE Journal - August 2011 - 40
ASHRAE Journal - August 2011 - 41
ASHRAE Journal - August 2011 - 42
ASHRAE Journal - August 2011 - 43
ASHRAE Journal - August 2011 - Hospital Upgrade: Heat Recovery, Geothermal Save Energy
ASHRAE Journal - August 2011 - 45
ASHRAE Journal - August 2011 - 46
ASHRAE Journal - August 2011 - 47
ASHRAE Journal - August 2011 - Cool Weather Savings: Using Hybrid Refrigeration Systems for Chiller Retrofit
ASHRAE Journal - August 2011 - 49
ASHRAE Journal - August 2011 - 50
ASHRAE Journal - August 2011 - 51
ASHRAE Journal - August 2011 - InfoCenter
ASHRAE Journal - August 2011 - 53
ASHRAE Journal - August 2011 - 54
ASHRAE Journal - August 2011 - 55
ASHRAE Journal - August 2011 - 56
ASHRAE Journal - August 2011 - 57
ASHRAE Journal - August 2011 - 58
ASHRAE Journal - August 2011 - 59
ASHRAE Journal - August 2011 - 60
ASHRAE Journal - August 2011 - Solar NZEB Project
ASHRAE Journal - August 2011 - 62
ASHRAE Journal - August 2011 - 63
ASHRAE Journal - August 2011 - 64
ASHRAE Journal - August 2011 - 65
ASHRAE Journal - August 2011 - Emerging Technologies
ASHRAE Journal - August 2011 - 67
ASHRAE Journal - August 2011 - 68
ASHRAE Journal - August 2011 - 69
ASHRAE Journal - August 2011 - 70
ASHRAE Journal - August 2011 - 71
ASHRAE Journal - August 2011 - 72
ASHRAE Journal - August 2011 - 73
ASHRAE Journal - August 2011 - 74
ASHRAE Journal - August 2011 - Special Products
ASHRAE Journal - August 2011 - IAQ Applications
ASHRAE Journal - August 2011 - 77
ASHRAE Journal - August 2011 - 78
ASHRAE Journal - August 2011 - 79
ASHRAE Journal - August 2011 - Washington Report
ASHRAE Journal - August 2011 - 81
ASHRAE Journal - August 2011 - People
ASHRAE Journal - August 2011 - 83
ASHRAE Journal - August 2011 - Products
ASHRAE Journal - August 2011 - 85
ASHRAE Journal - August 2011 - Classified Advertising
ASHRAE Journal - August 2011 - 87
ASHRAE Journal - August 2011 - Advertisers Index
ASHRAE Journal - August 2011 - Cover3
ASHRAE Journal - August 2011 - Cover4
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