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ASHRAE 94.2 Method of Testing Thermal Storage Devices with Electrical Input and Thermal Output Based on Thermal Performance, 2010
- 94.2_2010_text.pdf [Go to Page]
- FOREWORD
- 1. PURPOSE
- 2. SCOPE
- 2.1 This standard applies to thermal storage devices that are charged electrically and discharged thermally. The energy may be stored as latent heat or as sensible heat or as a combination of the two.
- 2.2 The device is charged by electric-resistance heating, and the electric-resistance mechanism is an integral part of, or is located inside, the storage device.
- 2.3 The device is discharged by a heat transfer fluid that enters the device through a single inlet and leaves the device through a single outlet. Storage devices having more than one inlet and/or outlet may be tested according to this standard, but ...
- 2.4 This standard does not include factors relating to cost, life, reliability, or the consideration of requirements for interfacing with specific heating and cooling systems.
- 2.5 The test procedure and equipment outlined in this standard are most easily adaptable to devices used to store thermal energy on the order of l011 J (108 Btu) or less.
- 3. DEFINITIONS
- 4. CLASSIFICATIONS
- 4.1 Sensible heat-type storage devices are those in which the heat absorbed by or removed from the system results in an increase or decrease in the temperature of the storage medium, and there is no change of phase of any portion of the storage mediu...
- 4.2 Latent heat-type storage devices are those involving a change of phase of the storage medium. In this type of storage device, most of the heat added to or removed from the system goes into changing the enthalpy of the storage medium during a chan...
- 4.3 Central thermal storage devices are those in which the output is ducted or piped from the device in a “central” location to the space or to heat transfer devices.
- 4.4 Room thermal storage devices are those in which the storage device is installed within a space or room. The output from the device may be by radiation from the cabinet, by natural convection through the device, by forced convection through the de...
- 5. REQUIREMENTS
- 5.1 Latent heat-type storage devices evaluated under this standard shall have been completely cycled (see definition of cycling) through their change of phase at least 30 times prior to being tested.
- 5.2 The transfer fluid used in evaluating the performance of a thermal energy storage device shall have a known specific heat that varies by less than ±0.5% over the temperature range encountered during a test.
- 5.3 The room where the testing of the storage device is performed shall have its temperature controlled to the extent that the average ambient air temperature, ta, determined by the average of the four temperatures measured as specified in Section 8....
- 6. INSTRUMENTATION
- 6.1 Temperature Measurements
- 6.2 Liquid Flow Measurements. The accuracy of the flow- measuring and associated readout devices shall be equal to or better than ±1.0% of the measured value.
- 6.3 Airflow Measurements. When air is used as the transfer fluid, airflow rate shall be determined as described in Section 7 using instrumentation described in ANSI/ASHRAE Standard 373 and ANSI/ASHRAE Standard 70.4
- 6.4 Pressure Measurements
- 6.5 Time and Mass Measurements. Time measurements and mass measurements shall be made to an accuracy of +0.20% for calibration purposes, see ANSI/ASHRAE Standard 37.3
- 6.6 Electrical Measurements. Electrical measurements shall be made with indicating instruments whose accuracy is within ±1.0% of the value being observed.
- 7. APPARATUS AND METHOD OF TESTING
- 7.1 Air as the Transfer Fluid (Central Devices)
- 7.2 Liquid as the Transfer Fluid (Central Type Devices)
- 7.3 Calorimeter (Room Type Devices)
- 7.4 Calibration. The calorimeter shall be calibrated so that the capacity of room-type devices can be determined from temperature and fan speed measurements.6
- 8. CENTRAL THERMAL STORAGE DEVICE TESTING
- 8.1 Preconditioning Test
- 8.2 Initial Charge Test
- 8.3 Maximum Standby Emission Test
- 8.4 Discharge Test (Device with Integral Fan or Pump)
- 8.5 Calculations. To evaluate the device performance, the following calculations shall be made.
- 8.6 Measurement of Ambient Air Temperature. The ambient air temperature, ta, shall be the arithmetic average temperature of the test area, determined by four calibrated temperature sensors. ANSI/ASHRAE Standard 41.11 shall be followed in making these...
- 9. ROOM THERMAL STORAGE DEVICE TESTING
- 9.1 Preconditioning Test. The purpose, performance, and measurements for this test are specified in Section 8.1.
- 9.2 Static Discharge Test
- 9.3 Dynamic Discharge Test
- 9.4 Calculations. The electrical power, P, shall be determined for each test condition from the calorimeter calibration curve developed in accordance with Section 7.4. By entering the curve with the measured temperature difference across the calorime...
- 10. DATA TO BE RECORDED AND TEST REPORT
- 10.1 Central Thermal Storage Devices
- 10.2 Room Thermal Storage Devices
- 11. NOMENCLATURE
- 12. REFERENCES
- Informative Annex A [Go to Page]