ASHRAE 4843-2006 Effect of Data Availability on Modeling of Residential Air Conditioners and Heat Pumps for Energy Calculations《节能计算(RP-1197)的建模住宅空调和热泵可用性数据效果》.pdf
《ASHRAE 4843-2006 Effect of Data Availability on Modeling of Residential Air Conditioners and Heat Pumps for Energy Calculations《节能计算(RP-1197)的建模住宅空调和热泵可用性数据效果》.pdf》由会员分享,可在线阅读,更多相关《ASHRAE 4843-2006 Effect of Data Availability on Modeling of Residential Air Conditioners and Heat Pumps for Energy Calculations《节能计算(RP-1197)的建模住宅空调和热泵可用性数据效果》.pdf(12页珍藏版)》请在麦多课文档分享上搜索。
1、4843 (RP-1197) Effect of Data Availability on Modeling of Residential Air Conditioners and Heat Pumps for Energy Calculations Michael R. Wassmer Associate Member ASHRAE ABSTRACT A component-based model for residential air conditioner and heat pump energy calculations has been developed through ASHRA
2、E Research Project 1197. A primary objective of this project was to develop a suitable model that requires only readily available, or potentially readily available, input data. The component model meets this objective by only requir- ing rating data that are generated from ARIStandard 21 01240. Unfo
3、rtunately, only a small percentage of the data collected during these tests is published by ARI. Some manufacturers releuse u more signijcuntportion of the test dutu in their tech- nical literature, but these data are often incomplete. This paper describes the development of default data for the mod
4、eling of residential air conditioners and heat pumps using a test suite of 25 units. The paper evaluates the impact of limited data availability, and the need to use default data, on modelpredic- tion accuracy. The results show that the use of minimal data open produces acceptable results, though ac
5、curacy improves sign$cantly with additional rating data. Of most importance are the power at standard rating conditions, the type of compressol; and the coil airflow rates. The results also show that accurate results are obtained without knowing the exact compressor model number: INTRODUCTION Comput
6、erized energy calculations are now routinely used for evaluating equipment alternatives during engineering design and specification. However, this application is less accurate and efficient than possible due to limitations in avail- able equipment simulation models and a mismatch between input requi
7、red by those models and the data published by Michael J. Brandemuehl, PhD, PE Member ASHRAE manufacturers. These shortcomings are particularly signifi- cant in residential energy analysis when it is desired to compare specific equipment alternatives in a particular build- ing and climate. A new mode
8、l for residential air conditioner and heat pump energy calculations was recently developed under ASHRAE Research Project 1197, Updated Energy Calcula- tion Models for Residential HVAC Equipment (Brandemuehl and Wassmer 2005). The new model, referred to here as the “component model,” is fundamentally
9、 different from the models currently residing in the most popular state-of-the-art whole building energy analysis programs. Almost ali current models use minimal equipment performance at standard conditions and regression equations based on the performance characteristics of typical equipment (e.g.,
10、 Winkelmann et al. 19931). The component model also requires equipment performance at standard conditions, but it uses a combination of first-principle models and empirical models of the primary system components to calculate the performance of the actual equipment at nonstandard operating condition
11、s. Its combina- tion of accuracy and minimal input requirements make the component model an updated alternative to the current models in building energy analysis programs. Application of any HVAC equipment model, including the component model, requires data on equipment character- istics. In the abs
12、ence of such equipment characteristics, users are forced to use default values to fill the voids. This paper explores the availability and quality of data required by the component model, the development of default data, the effects of poor rating data on the results, and suggestions for future rati
13、ng data standards to maximize the performance of energy simulation models and their ease of use. Michael R. Wassmer is an engineer at the National Renewable Energy Laboratory, Golden, Colo. Michael J. Brandemuehl is an associate professor in the Department of Civil, Environmental, and Architectural
14、Engineering, University of Colorado at Boulder. 21 4 02006 ASHRAE. COMPONENT MODEL The component model consists of a combination of first- principle and empirical models of individual direct expansion (DX) system components (Wassmer and Brandemuehl 2005). Given models of the compressor, condenser, e
15、vaporator, and expansion device, energy and mass balances are performed on the vapor compression cycle using simplified refrigerant prop- erties (Bourdouxhe et al. 1996). The compressor model is an empirically and statistically based correlation for positive displacement compressors. The model has p
16、olynomial fits for the refrigerant mass flow rate, mrer, and the power draw of the compressor, Pcomp. There are two independent variables in each ten-tem equation. They are the saturated suction temperature, SSZ and the saturated discharge temperature, SDT = M, +M2ssT+M3sDT+Mqss+M5(ssT)(sDT)+MgsD mr
17、ef; rated + M,SS? + M(SDT)(SS?) + M(SST)(SD?) + MSD? (1) camp = pl +P2SST+P3SDT+PqSS12+P5(SST)(SDT)+PgSD? + P,SS? + P,(SDTXSS?) + P,(SST)(SD?) + P,SD? comp,rafed (2) The rating conditions and form of the equations are spec- ified by AR1 Standard 540 (AR1 1999). Specifically, the rated flow rate and
18、power are determined at SST= 45F (7.2“C) and SDT= 130F (54.4“C). The coefficients are typically available directly from the manufacturers. The condenser is simulated using an air-to-liquid coil model that accounts for heat transfer between air and a liquid through a dry-finned coil surface. The mode
19、l is based on simple effectiveness-NTU heat exchanger relationships, described in most introductory heat transfer textbooks, and assumes that the temperature of the refrigerant throughout the coil is fixed at the SDT. The evaporator is also modeled using effectiveness-NTU relationships. For heat pum
20、ps, the same dry coil model is used. For air conditioners, the model is modified to account for both the heat and mass transfer of the cooling and dehumidifying coil (Threlkeld 1970; Brandemuehl et al. 1993). The model also assumes that the refrigerant temperature is constant at the SST through the
21、coil. The vapor compression system component models describe the steady-state performance of the system. Useful energy calculation models of residential HVAC equipment are obtained by modifiing the steady-state models to account for part-load cycling, the effects of fan power and heat, and in the ca
22、se of heat pumps, defrosting and crank-case heaters. The results of the model include the average power consumption of the compressor, indoor and outdoor fans, and ancillary equip- ment, as well as the temperature and humidity of the air deliv- ered to the building and the average run-time fraction
23、of the system. DATA REQUIREMENTS AND AVAILABILITY All energy calculation models for residential HVAC equipment rely on published data to describe the performance of the equipment being modeled. Some models require a map of performance over a range of psychrometric conditions and airflow rates to obt
24、ain regression curves. Since the component model uses first-principle relationships, it requires less infor- mation to identie the model parameters. In fact, given the compressor rating data, the steady-state model parameters can be identified using performance data at a single system oper- ating co
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