ARI-770-2001-REFRIGERANT PRESSURE REGULATING VALVES by Navid Anari

2001 STANDARD for

REFRIGERANT PRESSURE REGULATING VALVES

Standard 770 4301 NORTH FAIRFAX DRIVE

•

ARLINGTON, VIRGINIA 22203

IMPORTANT

SAFETY RECOMMENDATIONS It is strongly recommended that the product be designed, constructed, assembled and installed in accordance with nationally recognized safety requirements appropriate for products covered by this standard. ARI, as a manufacturers' trade association, uses its best efforts to develop standards employing state-of-the-art and accepted industry practices. However, ARI does not certify or guarantee safety of any products, components or systems designed, tested, rated, installed or operated in accordance with these standards or that any tests conducted under its standards will be non-hazardous or free from risk.

Note: This standard supersedes ARI Standard 770-94.

Price $15.00 (M) $30.00 (NM) Printed in U.S.A.

TABLE OF CONTENTS SECTION

PAGE

Section 1.

Purpose ...............................................................................................................1

Section 2.

Scope ..................................................................................................................1

Section 3.

Definitions ..........................................................................................................1

Section 4.

Test Requirements ..............................................................................................2

Section 5.

Rating Requirements ..........................................................................................2

Section 6.

Minimum Data Requirements for Published Ratings.........................................2

Section 7.

Marking and Nameplate Data.............................................................................3

Section 8.

Conformance Conditions....................................................................................3 APPENDICES

Appendix A.

References - Normative......................................................................................4

Appendix B.

References - Informative ....................................................................................4

Appendix C.

Method of Testing for Rating Refrigerant Pressure Regulating Valves - Normative ..........................................................................5 TABLES FOR APPENDICES

Table C1.

Pressure-Tap Hole Diameters and Lengths ........................................................8

Table C2.

Specific Heat Ratios (k)....................................................................................14 FIGURES FOR APPENDICES

Figure C1.

Typical System Piping for Pressure Regulating Valve Liquid Flow Test .........6

Figure C2.

Typical System Piping for Pressure Regulating Valve Gas Flow Test ..............7

Figure C3.

Mass Flow Rate vs. Density C Pressure Drop...................................................11

Figure C4.

KA vs. Acoustic Ratio.......................................................................................13

ARI STANDARD 770-2001

REFRIGERANT PRESSURE REGULATING VALVES Section 1. Purpose

3.4 Main. Tubing or piping by which the Refrigerant Pressure Regulating Valve is connected to the apparatus.

1.1 Purpose. The purpose of this standard is to establish, for Refrigerant Pressure Regulating Valves: definitions; test requirements; rating requirements; minimum data requirements for Published Ratings; marking and nameplate data; and conformance conditions. 1.1.1 Intent. This standard is intended for the guidance of the industry, including manufacturers, engineers, installers, contractors and users. 1.1.2 Review and Amendment. This standard is subject to review and amendment as technology advances. Section 2. Scope 2.1 Scope. This standard applies to Refrigerant Pressure Regulating Valves controlling Volatile Refrigerant flow that primarily respond to pressure. The types of Refrigerant Pressure Regulating Valves are those that are responsive to inlet, to outlet, or to differential pressures sensed locally or remotely. 2.2 Exclusions. Excluded from this standard are Automatic Expansion Valves and devices used with: a. b. c.

Automotive and recreational conditioning Household refrigerating units Room air-conditioners

vehicle

air-

All terms in this document shall follow the standard industry definitions in the current edition of ASHRAE Terminology of Heating, Ventilation, Air Conditioning and Refrigeration unless otherwise defined in this section. liquid

3.6 Published Rating. A statement of the assigned values of those performance characteristics under stated Rating Conditions, by which a Refrigerant Pressure Regulating Valve may be chosen to fit its application. These values apply to all Refrigerant Pressure Regulating Valves of like nominal size and type produced by the same manufacturer. As used herein, the term Published Rating includes the rating of all performance characteristics shown on the Refrigerant Pressure Regulating Valve or published specifications, advertising or other literature controlled by the manufacturer, at stated Rating Conditions. 3.6.1 Application Rating. A rating based on tests performed at Application Rating conditions (other than Standard Rating Conditions). 3.6.2 Standard Rating. A rating based on tests performed at Standard Rating Conditions. 3.7 Rating Conditions. Any set of operating conditions under which a single level of performance results, and which cause only that level of performance to occur. 3.7.1 Standard Rating Conditions. Rating Conditions used as the basis of comparison for performance characteristics.

Section 3. Definitions

3.1 Bubble Point. Refrigerant temperature at a specified pressure.

3.5 Pressure Drop. The pressure difference between the Refrigerant Pressure Regulating Valve inlet and the Refrigerant Pressure Regulating Valve outlet, with the main port (orifice) open, psi [kPa].

saturation

3.2 Dew Point. Refrigerant vapor saturation temperature at a specified pressure. 3.3 Gradient. The change in controlled pressure required to move the Refrigerant Pressure Regulating Valve closure member from its opening point to its standard rated capacity, psi [kPa]. In some types of pilot-operated controllers, the Gradient could be essentially zero.

3.8 Refrigerant Pressure Regulating Valve. A self or pilot-operated controller in which the energy to position the Refrigerant Pressure Regulating Valve closure member is provided by the pressure of the controlled refrigerant, sensed locally or remotely. 3.8.1 Differential Pressure Regulating Valve. A valve which opens or closes in response to a difference in pressure between the inlet and outlet, sensed locally or remotely. 3.8.2 Downstream Pressure Regulating Valve. A valve which opens or closes in response to a change in outlet pressure, sensed locally or remotely. 3.8.3 Upstream Pressure Regulating Valve. A valve which opens or closes in response to a change in inlet pressure, sensed locally or remotely.

ARI STANDARD 770-2001 3.8.4 Valve Closure Member. The part of a valve which is positioned to close, open or modulate the flow through the valve port(s). 3.9 Refrigerant Pressure Regulating Valve Capacity. The mass flow rate of a fluid through the Refrigerant Pressure Regulating Valve, expressed in suitable units for the application and based on specific conditions. 3.10 Set Point. A predetermined pressure which the Refrigerant Pressure Regulating Valve is set to maintain, psi [kPa]. 3.11 "Shall" or "Should." "Shall" or "should" shall be interpreted as follows: 3.11.1 Shall. Where “shall” or “shall not” is used for a provision specified, that provision is mandatory if compliance with the standard is claimed. 3.11.2 Should. “Should” is used to indicate provisions which are not mandatory but which are desirable as good practice. 3.12 Volatile Refrigerant. A fluid used for heat transfer in a refrigerating system which absorbs heat at a low temperature and low pressure of the fluid and transfer heat at a higher temperature and a higher pressure of the fluid, usually involving changes of state of the fluid. Section 4. Test Requirements 4.1 Capacity Tests. All Refrigerant Pressure Regulating valve Capacity tests shall be in accordance with the test procedure outlined in Appendix C.

40oF [4.4oC] c.

Discharge Gas Service Temperature: Superheated refrigerant vapor at a temperature based on 5.2.4

5.2.2 Expansion Point Enthalpy (hf). Enthalpy based on 100oF [37.8oC] saturated liquid (Bubble Point) refrigerant entering the expansion valve. 5.2.3 Enthalpy of the Refrigerant Suction Gas (hg). Enthalpy based on vapor at Dew Point pressure corresponding to 40oF [4.4oC] leaving the evaporator. 5.2.4 Discharge Gas Temperature. The temperature that would result from isentropic compression from the saturated evaporator (Dew Point) temperature with 25.0oF [13.9oC] superheat, to a saturated condensing (Bubble Point) temperature of 100oF [37.8oC] with 50.0oF [27.8oC] added as an approximation of the actual polytropic refrigerant compression process. 5.2.5 Gradient. Every Published Capacity Rating shall be based on the capacity resulting from a pressure change above or below the Set Point where applicable. The maximum pressure change upon which the rating is based shall be clearly designated. 5.3 Application Rating. Application Ratings give performance data under operating conditions other than those given above. Applications Ratings shall contain all information shown in 6.2. Published Ratings shall be subject to the tolerances of this standard. 5.4 Tolerances. To comply with this standard, measured test results shall not be less then 95% of Published Capacity Rating.

Section 5. Rating Requirements 5.1 Rating Requirements. Published Capacity Ratings shall consist of Standard Ratings and may include Application Ratings. The ARI Standard Ratings of Refrigerant Pressure Regulating Valve Capacity shall be stated in tons of refrigeration [kW] and at the conditions specified in 5.2. 5.2

Standard Rating Conditions. 5.2.1 Refrigerant Pressure Regulating Valve Entrance Conditions.

Liquid Service Temperature: 101°F [38.3oC] saturated liquid refrigerant

Suction Service Temperature: 65°F [18oC] superheated refrigerant vapor at the saturation pressure corresponding to

Section 6. Minimum Data Requirements for Published Ratings 6.1 Minimum Data Requirements for Published Ratings. As a minimum, Published Ratings shall include all Standard Ratings. All claims to ratings within the scope of this standard shall include the statement “Rated in accordance with ARI Standard 770”. All claims to ratings outside the scope of this standard shall include the statement “Outside the scope of ARI Standard 770”. Wherever Applications Ratings are published or printed, they shall include a statement of the conditions at which the ratings apply.

ARI STANDARD 770-2001 6.2 Published Ratings. Published Ratings shall include the following information: a. b. c. d. e. f. g. h.

Set Point adjustment range, psi [kPa] Refrigerant designation(s) per ANSI/ASHRAE 34 with Addenda Fluid state (liquid or gas) Capacity at Standard Rating Conditions, tons [kW] Pressure Drop across valve (at Standard Rating Conditions), psi [kPa] Gradient at Rated Conditions Model designation, line connections (size and type) Manufacturer's name and address

Section 7. Marking and Nameplate Data 7.1 Marking and Nameplate Data. As a minimum, each Refrigerant Pressure Regulating Valve shall be marked with the following information: a. b. c.

The manufacturer's name or trade name Model designation Refrigerant designation(s) per ANSI/ASHRAE Standard 34 with Addenda Section 8. Conformance Conditions

8.1 Conformance. While conformance with this standard is voluntary, conformance shall not be claimed or implied for products or equipment within its Purpose (Section 1) and Scope (Section 2) unless such claims meet all of the requirements of the standard.

ARI STANDARD 770-2001

APPENDIX A. REFERENCES - NORMATIVE A1 Listed here are all standards, handbooks and other publications essential to the formation and implementation of the standards. All references in this appendix are considered as part of the standard.

A1.3 ANSI/ASHRAE Standard 41.3-89 Standard Method for Pressure Measurement, 1989, American Society of Heating, Refrigerating, and AirConditioning Engineers, Inc., 1791 Tullie Circle N.E., Atlanta, GA 30329, U.S.A.

A1.1 ANSI/ASHRAE Standard 34-2001 with Addenda, Designation and Safety Classification of Refrigerants, 2001, American Society of Heating, Refrigerating, and Air-Conditioning Engineers, Inc., 1791 Tullie Circle N.E., Atlanta, GA 30329, U.S.A.

A1.4 2001 ASHRAE Handbook - Fundamentals, American Society of Heating Refrigerating and AirConditioning Engineers, Inc., 1791 Tullie Circle N.E., Atlanta, GA 30329, U.S.A.

A1.2 ANSI/ASHRAE Standard 41.1-86 Standard Method for Temperature Measurement, 1986, American Society of Heating, Refrigerating, and AirConditioning Engineers, Inc., 1791 Tullie Circle N.E., Atlanta, GA 30329, U.S.A.

A1.6 ASHRAE Terminology of Heating, Ventilation, Air Conditioning and Refrigeration, Second Edition, 1991, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., 1791 Tullie Circle N.E., Atlanta, GA 30329, U.S.A.

APPENDIX B. REFERENCES - INFORMATIVE B1 Listed here are standards, handbooks and other publications which may provide useful information and background but are not considered essential. References in this appendix are not considered part of the standard.

B1.3 ASME Fluid Meters. Their Theory and Application, Sixth Edition, 1971, American Society of Mechanical Engineers, 345 East 47th Street, New York, NY 10017, U.S.A.

B1.1 ASHRAE Handbook - HVAC Systems and Equipment, 2000, American Society of Heating Refrigerating and Air-Conditioning Engineers, Inc., 1791 Tullie Circle N.E., Atlanta, GA 30329, U.S.A.

B1.4 Flow Characteristics of Solenoid Valves Report No. 3 â&#x20AC;&#x201C; Final Report, dated January 1970, a thesis submitted by George T. Kartsounes to the Faculty of Purdue University, West Lafayette, IN 47907-1077.

B1.2 ASHRAE Refrigerant Line Sizing RP185, 1977, American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., 1791 Tullie Circle N.E., Atlanta, GA 30329, U.S.A.

ARI STANDARD 770-2001

APPENDIX C. METHOD OF TESTING FOR RATING REFRIGERANT PRESSURE REGULATING VALVES NORMATIVE C1

gravity, by pump or by pressurized tank of adequate capacity, and equipped with a suitable pressure reducing device. Other essential apparatus which shall be used are covered in C3.2.

Method of Test. C1.1

Flow Capacity. C1.1.1 The Refrigerant Pressure Regulating Valves shall be tested in a fluid flow loop with instrumentation per C2 and apparatus per C3.

C3.1.2 Gas Flow Test. The Refrigerant Pressure Regulating Valve to be tested shall be installed in a system such as the one shown in Figure C2 where air flows through the valve by pressure from a suitably regulated pressure supply. Other essential apparatus which shall be used are covered in C3.2.

C1.1.2 The Refrigerant Pressure Regulating Valves shall be tested at various Pressure Drop values per C4 and the data shall be recorded per C5. C1.1.3 The Refrigerant Pressure Regulating Valve Capacity shall be calculated per the method of C6. C2

Instruments. C2.1 General. Instruments shall have the accuracies listed in this section and shall be calibrated against certified standards. C2.2 Temperature Measuring Instruments. All temperature-measuring instruments shall be calibrated per ANSI/ASHRAE 41.1. C2.3 Pressure Measuring Instruments. All pressure measuring instruments shall be calibrated per ANSI/ASHRAE 41.3. C2.4

Fluid Flow Measuring Instruments. C2.4.1 All fluid flow measuring instruments shall be accurate within 2.0% of the reading, throughout the range of flows measured. C2.4.2 In no case shall the smallest scale division of the measuring instrument exceed 2.5 times the specified accuracy.

Apparatus. C3.1

C3.2

Other Essential Apparatus. C3.2.1 Instrumentation. Suitable instrumentation shall be chosen for measuring temperature (C2.2), pressure (C2.3) and flow (C2.4). C3.2.2 Main Size. The pipe or tubing, used for the inlet and outlet connecting Mains to the Refrigerant Pressure Regulating Valve being tested, shall be Schedule 40 Wrought Iron or Steel Pipe, or Type L Hard Drawn Copper Tubing. The Main size shall be the same size and type provided by the Refrigerant Pressure Regulating Valve body connections. In the case of solder type body connections, which are machined to use with either of two sizes of tubing, the smaller size shall govern the Main size for test purposes. The Main shall be free from scale, rust, or other obstructions that may cause excessive turbulence. C3.2.3 Main Length. The inlet and outlet Mains, connected to the Refrigerant Pressure Regulating Valve being tested, shall be straight for a minimum of fourteen internal Main diameters from the face of the Refrigerant Pressure Regulating Valve inlet and outlet connections, respectively.

Flow Tests. C3.1.1 Liquid Flow Test. The Refrigerant Pressure Regulating Valve to be tested shall be installed in a system such as the one shown in Figure C1, where water flows through the valve by pressure supplied by

ARI STANDARD 770-2001

Figure C1. Typical System Piping for Pressure Regulating Valve Liquid Flow Test

ARI STANDARD 770-2001

Figure C2. Typical System Piping for Pressure Regulating Valve Gas Flow Test

ARI STANDARD 770-2001 Table C1. Pressure- Tap Hole Diameters and Lengths Main Type and Size Pressure - Tap Hole Minimum Length from the Nominal Pipe Size Tube Size - OD Diameter Internal Surface of the Main in in mm in mm in mm 1/8 - 1/4 3/16 - 3/8 4-10 1/32 0.8 1/16 1.6 3/8 1/2 12 3/64 1.2 3/32 2.4 1/2 5/8 - 3/4 16 - 20 1/16 1.6 1/8 3.2 3/4 7/8 22 5/64 2 5/32 4.0 1 1-1/8 28 3/32 2.4 3/16 4.8 1-1/4 1-3/8 35 1/8 3.2 1/4 6.3 1-1/2 1-5/8 42 5/32 4 5/16 7.9 2 2-1/8 54 3/16 4.8 3/8 9.5 C3.2.4 Pressure-Tap Holes. C3.2.4.1 It is necessary to locate the pressure-tap holes at the proper points. With vertical Mains, the points on the circumference of the Main at which the holes will be drilled will depend on the position of the Main with respect to adjacent surroundings. With horizontal Mains, the position of the holes on the circumference of the Main depends largely on the fluid being carried in the Main, and somewhat on the available clearance and the position of any bends preceding the holes. With liquids, it is desirable to have the holes level with or below the centerline of the Main. It is not advisable to place the holes near the bottom if there is any possibility of their becoming clogged with sediment. Extreme care shall be exercised in providing pressure-tap holes in the wall of the Main in order to avoid errors due to impact and eddies. The character of the Main adjoining the holes shall be such as to insure that the flow is parallel to the wall. There shall be no rivet heads, jogs or other sources of eddies nearby. The pressure-tap holes shall be drilled radial and perpendicular to the axis of the Main and should be on the same side with their axes parallel. The holes shall be

straight, and of uniform size, for a length from the inner surface of the Main equal to at least two hole diameters. Additional material shall be affixed to the Main if the Main has a wall thickness less than two hole diameters. The inner rim of the hole shall be flush with the inner surface of the Main, shall have no burrs or jagged edges and shall be slightly rounded to make smoothness more certain. Table C1 lists the pressure-tap hole diameters and lengths, which shall be used in various sizes of Mains. C3.2.4.2 The upstream pressuretap hole shall be located in the Main, two internal Main diameters upstream from the face of the inlet connection of the Refrigerant Pressure Regulating Valve being tested. C3.2.4.3 The downstream pressure-tap hole shall be located in the Main, ten internal Main diameters downstream from the face of the outlet connection of the Refrigerant Pressure Regulating Valve being tested. C3.2.5 Fluid Temperature Measurement Locations. Measurement of the temperature of the fluid entering the Refrigerant Pressure Regulating Valve, when required, shall be made at a point located not over twelve internal Main diameters upstream

ARI STANDARD 770-2001 from the face of the inlet connection of the Refrigerant Pressure Regulating Valve being tested. C4

C4.2.1 The Refrigerant Pressure Regulating Valve shall be tested on an airflow system with instrumentation in accordance with Section C2 and apparatus in accordance with C3.1.2.

Test Procedure.

C4.2.2 The test shall consist of the following procedures:

C4.1 Liquid Flow Capacity Test. All tests for liquid flow capacity shall be conducted in the following manner:

C4.2.2.1 Adjust the Refrigerant Pressure Regulating Valve to its opening point within "0.5 psig [3 kPa gage]. Change the controlled pressure by the amount of the rated Gradient for the Refrigerant Pressure Regulating Valve.

C4.1.1 The Refrigerant Pressure Regulating Valve shall be tested on a water flow system with instrumentation in accordance with C2 and apparatus in accordance with C3.1.1. C4.1.2 The test shall consist of the following procedures:

C4.2.2.2 Measure flow across the Refrigerant Pressure Regulating Valve at ten evenly dispersed Pressure Drop values

C4.1.2.1 Adjust the Refrigerant Pressure Regulating Valve to its opening point within "0.5 psig [3 kPa gage]. Change the controlled pressure by the amount of the rated Gradient for the Refrigerant Pressure Regulating Valve.

(∆p's) with ªp/P1A # 0.1 at the inlet of the valve being tested.

C4.2.2.3 Measure flow across the Refrigerant Pressure Regulating Valve at ten evenly dispersed Pressure Drop values

C4.1.2.2 Gradually adjust the Pressure Drop across the Refrigerant Pressure Regulating Valve. The complete test shall consist of a range of Pressure Drop values varying from 1 psi [7 kPa] to 10 psi [70 kPa], in 1 psi [7 kPa] increments.

(ªp's) with 0.1 # ªp/P1A # 0.5 at the inlet of the valve being tested. C4.2.2.4 The test shall be run at increasing Pressure Drop and decreasing Pressure Drop, at the same Pressure Drop values in C4.2.2.2 and C4.2.2.3. A higher reading shall not vary from the corresponding lower reading by more than 3.0% of the lower value. The mean of the two values shall be considered to be the reading used for calculations.

C4.1.2.3 The test shall consist of ten test values at increasing Pressure Drop, and ten test values at decreasing Pressure Drop, incremented as in C4.1.2.2. A higher reading shall not vary from the corresponding lower reading by more than 3.0% of the lower value. The mean of the two values shall be considered the reading to be recorded.

C4.2.2.5 Record data in accordance with C5 after each reading. C5

C4.1.2.4 Record data in accordance with C5 after each reading. C4.2 Gas Flow Capacity Test. All tests for gas flow capacity shall be conducted in the following manner:

Data to be Recorded. C5.1

General Data. a. b.

Date Observers

ARI STANDARD 770-2001 C5.2 Refrigerant Pressure Regulating Valve Descriptive Data.

C5.3

Manufacturer's name and address

Model designation, type, serial number, and size (record all that apply)

Flow Test Data. C5.3.1 Liquid Flow Test Data. a. b. c. d. e.

Valve inlet pressure, P1, psig [kPa gage] Valve inlet temperature, EF [EC] Pressure Drop across valve, psi [kPa] Mass flow rate through valve, lb/min [kg/s] Barometric pressure, in Hg [kPa]

C5.3.2 Gas Flow Test Data. a. b. c. d.

e. C6

Valve inlet pressure, P1, psig [kPa gage] Valve inlet temperature, EF [EC] Pressure Drop across valve, psi [kPa] Flow through valve 1. Mass flow rate, lb/min [kg/s] 2. Volume rate of flow, ft3/min [m3/s] Barometric pressure, in Hg [kPa]

Capacity Calculations. C6.1

Liquid Refrigerant Flow Capacities. C6.1.1 The data from C5.3.1 shall be used to calculate the points for the Refrigerant Pressure Regulating Valve's mass flow rate curve. C6.1.1.1 Using the recorded water temperature at each test point, determine the water mass density, ρ, lb/ft3 [kg/m3], from the water properties table referenced in the 2001 ASHRAE Handbook Fundamentals. C6.1.1.2 Multiply the recorded Pressure Drop from each test point

by the corresponding water mass density, lb/ft3 [kg/m3], from C6.1.1.1. C6.1.1.3 Plot mass flow rate, lb/min [kg/s], as the ordinate, and the product of mass density times Pressure Drop (ρªp) as the abscissa, on a log-log graph as illustrated in Figure C3 C6.1.1.4 The water mass flowrate capacity, m& water , may now be found for any combination of density and Pressure Drop by computing ρªp and finding m& water from the graph. C6.1.2 List the following information regarding the Refrigerant Pressure Regulating Valve's rating point per C5. a. b. c. d. e. f.

Refrigerant Inlet pressure, P1, psig [kPa gage] Inlet temperature, EF [EC] Pressure Drop across valve, psi [kPa] Saturated evaporator temperature, EF [EC] Liquid temperature at the expansion device inlet, EF [EC]

C6.1.3 Determine the following information at the rating point from tables of refrigerant properties referenced in the 2001 ASHRAE Handbook - Fundamentals. C6.1.3.1 Refrigerant liquid mass density, D, lb/ft3 [kg/m3], at the temperature from C6.1.2.f. C6.1.3.2 Enthalpy of saturated refrigerant vapor, hg, Btu/lb [kWqs/kg], at the temperature from C6.1.2.e. C6.1.3.3 Enthalpy of refrigerant liquid, hf, Btu/lb [kWqs/kg] at the temperature from C6.1.2.f. C6.1.4 Multiply the Pressure Drop from C6.1.2.d by the refrigerant liquid mass density from C6.1.3.1 (ρªp).

ARI STANDARD 770-2001

Mass Flow Rate, lb/min [kg/s]

100

Square Root Function Line with Slope of 1/2

1 0.1

Density • Pressure Drop (D∆p), lb/ft3 x psi [kg/m3 x kPa]

This is an example plot

Figure C3. Mass Flow Rate vs Density • Pressure Drop

ARI STANDARD 770-2001 C6.1.5 Enter the abscissa on the Refrigerant Pressure Regulating Valve's mass flow rate curve (Figure C3) at the quantity (ρªp) calculated in C6.1.4 and locate the point of intersection with the mass flow rate curve. Proceed horizontally to the left and read the valve's refrigerant mass flow rate, m& , lb/min [kg/s]. C6.1.6 Calculate the refrigerant mass flow rate per unit capacity, (lb/min)/ton [(kg/s)/kW], at the rating point from the equations:

X hg − h f

(

)

where: X = A conversion constant, 200 (Btu/min)/ton [1] C6.1.7 Calculate the Refrigerant Pressure Regulating Valve Capacity, tons [kW], at the rating point from the following equation: m& C2 Q= M C6.2

C6.2.1 The data from C5.3.2 shall be used to calculate the Refrigerant Pressure Regulating Valve flow curves. C6.2.1.1 Convert the flow meter readings to mass flow rate units, lb/min [kg/s]. C6.2.1.2 Using the recorded inlet air temperature and inlet air pressure at each test point, determine the inlet air mass density, ρ, lb/ft3 [kg/m3]. C6.2.1.3 Calculate the value of KA at each test point from the equation:

m& N 2g ρ ∆p

C6.2.1.4 Calculate the acoustic ratio, R, for each test point from the equation:

∆p k ⋅ P1A

C6.2.1.5 Calculate the (ρªp) value for each test point. C6.2.1.6 Prepare Plot No. 1 for Pressure Drop values taken in C4.2.2.2. Plot the (ρªp) values as the abscissa and mass flow rate, m& , lb/min [kg/s], as the ordinate on a log-log graph as illustrated in Figure C3. C6.2.1.7 Prepare Plot No. 2 for Pressure Drop values taken in C4.2.2.3. Plot the R values as the abscissa and KA values as the ordinate on a linear coordinate graph as illustrated in Figure C4. C6.2.2 List the following information regarding the Refrigerant Pressure Regulating Valve's rating point as per C5: a. b. c. d.

Gas Refrigerant Flow Capacities.

KA =

e. f.

C6.2.3 Determine the following information at the rating point from tables of refrigerant properties referenced in 2001 ASHRAE Handbook - Fundamentals, Chapter 17. C6.2.3.1 Refrigerant mass density, D, lb/ft3 [kg/m3], at the temperature from C6.2.2.c. C6.2.3.2 Enthalpy of saturated refrigerant vapor, hg, Btu/lb [kJ/kg], at the temperature from C6.2.2.e. C6.2.3.3 Enthalpy of refrigerant liquid, hf, Btu/lb [kJ/kg], at the temperature from C6.2.2.f.

ARI STANDARD 770-2001

0.17

0.16

Figure C4. K·A vs. Acoustic Ratio

KA, in2 [mm2]

0.15

0.14

Curve Fit Through Data Points

0.13

0.12

0.11

0.1

Lowest Data Point

0.09

0.08

0.07 0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.07

Acoustic Ratio (R), ∆p/kqP1A

This is an example plot

Figure C4. KA vs. Acoustic Ratio

ARI STANDARD 770-2001

Table C2. Specific Heat Ratios (k) Pressure

Temperature

Location

Refrigerant

psia kPa (for 40oF [4.4oC] sat.)

Suction Gas

R12 R22 R502 R134a R404A1 R407C1 R410A R507 R717

51.6 356 83.2 573 95.2 656 49.7 343 99.8 688 76.3 526 133 917 105 721 73.3 505 (for 100oF [37.8oC] sat.)

Discharge Gas

R12 R22 R502 R134a R404A2 R407C2 R410A R507 R717

132.0 210.6 230.8 139.0 249.7 236.9 331.6 257.6 211.9

907.0 1451 1591 958.0 1720 1633 2285 1776 1461

Specific Heat Ratio cp /cv

65 65 65 65 65 65 65 65 65

18 18 18 18 18 18 18 18 18

1.187 1.267 1.205 1.168 1.184 1.191 1.279 1.186 1.379

183 202 182 180 180 202 198 177 257

83.9 94.4 83.3 82.2 82.2 94.4 92.2 80.6 125

1.183 1.245 1.210 1.161 1.213 1.214 1.298 1.220 1.340

Notes: 1 Dew Point pressure used for suction conditions for zeotropes. 2 Bubble Point pressure used for discharge conditions for zeotropes. C6.2.3.4 Specific heat ratio, k, at the inlet pressure and temperature from C6.2.2.b and c, respectively. Values for commonly used volatile refrigerants are given in Table C2. C6.2.4 Using refrigerant values from C6.2 calculate: a. b.

ρªp R as defined in C6.2.4

C6.2.5 Values of R ≤ 0.07 from C6.2.4.b shall be applied to Figure C3 as shown in C6.2.5.1. C6.2.5.1 Enter the abscissa on Figure C3 as calculated in C6.2.4.a and locate the point of intersection with the mass flow rate curve. Proceed horizontally to the left and read the Refrigerant Pressure Regulating Valve's

refrigerant mass flow rate, lb/min [kg/s]. C6.2.6 Values of R > 0.07 from C6.2.4.b shall be applied to Figure C4. C6.2.6.1 Enter the abscissa on Figure C4 as calculated in C6.2.4.b and locate the point of intersection with the KA curve. Proceed horizontally to the left and read the KA value. C6.2.6.2

Utilizing the formula:

m& = (KA) N

2g ρ∆ p

Calculate the mass rate of flow ( m& ) lb/min [kg/s].

ARI STANDARD 770-2001 C6.2.7 Calculate the refrigerant mass flow rate per unit capacity, (lb/min)/ton [(kg/s)/kW], at the rating point from the equations:

X M= (hg − h f )

where: X = A conversion constant, 200 (Btu/min)/ton [1]. C6.2.8 Calculate the Refrigerant Pressure Regulating Valve Capacity , tons [kW], at the rating point from the following equation:

m& Q= M

C7 Symbols and Subscripts. The symbols and subscripts used in Equations C1 through C7 are as follows:

Symbols. A cp

= =

hg = hf

K = KA = k = m& = M = N Îp P1 P1A Q R ρ

= = = = = = =

Valve port area, in2 [mm2] Specific heat at constant pressure, Btu/(lbAoF) [kJ/(kgAK)] Specific heat at constant volume, Btu/(lbAoF) [kJ/(kgAK)] Acceleration due to gravity, 32.2 ft/s2 [9.81 m/s2] Enthalpy of refrigerant vapor (Dew Point) at evaporator outlet, (Btu)/lb [kWqs/kg] Enthalpy of refrigerant liquid (Bubble Point) at expansion valve inlet, Btu/lb [kWqs/kg] Inlet flow coefficient Product of inlet flow coefficient and valve port area, in2 [mm2] Specific heat ratio Refrigerant mass flow rate, lb/min [kg/s], unless noted otherwise Refrigerant mass flow rate per unit capacity, (lb/min)/ton [(kg/s)/kW] Conversion constant, 5 [1.0096x10-5] Pressure Drop across valve, psi [kPa] Valve inlet pressure, psig [kPa gage] Valve inlet pressure, psia [kPa absolute] Capacity, tons [kW] Acoustic ratio Mass density, lb/ft3 [kg/m3]