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The validation process and result of a dynamic air handling unit (AHU) model (referred to as 1312 model hereafter) are discussed in this paper. The development of the 1312 model is summarized in a companion paper. Strategies to validate the model using experimental data mostly from common system operations are designed. If problems were identified using system operation data, follow up component model calibration is used to modify and improve the model. A series of experiments were designed and implemented to obtain pressure resistance parameters for the supply duct system and mixing box dampers. Building operation data from winter, summer, and spring seasons were used to validate the 1312 model. Good agreements were achieved between experimental data and simulation outputs for the 1312 AHU model, especially for summer and winter seasons. When using 1312 model to simulate AHU operation for spring season conditions, simulated outdoor and supply airflow rates and supply air temperature, while tracking experimental data, showed certain level of oscillation. [ABSTRACT FROM AUTHOR]

A dynamic air handling unit (AHU) simulation model that is capable of producing operational data for commonly used AHU configurations will assist further research in AHU control and operation, as well as fault detection and diagnosis. In this study, dynamic behaviors of an AHU and four building zones that were served by the AHU were modeled using HVACSIM+ software developed by the National Institute of Standards and Technology. The model (called 1312 model hereafter) was developed based on two previous ASHRAE projects (RP-825 and RP-1194). However, significant modifications, which included new parameters, new control strategies, and new component models, were made in this study to develop the 1312 model. The 1312 model structure, model parameter development process, and two new component models, namely a new coil valve model and a new fan energy model, are introduced in this paper. The new coil valve model considers nonlinear behaviors of a three way valve. The new fan energy model outputs fan energy consumption that includes energy consumptions for fan, belt, motor and VFD. Coefficients for the new fan energy model can directly be estimated from the total fan energy measurement. The 1312 model was also validated using real building operation data obtained from a large scale building laboratory facility. The validation process and results are introduced in a companion paper. [ABSTRACT FROM AUTHOR]

In this study, an energy balance and uncertainty analysis was performed on a standard chilled water cooling coil mounted in a commercial Air Handling Unit operating under typical conditions with a conventional PID loop control. Two different sets of relative humidity transmitters and temperature sensors (high and low accuracy) were evaluated for measuring relative humidity and temperature of the moist air entering and exiting a cooling coil. The impact of the different errors in these sensors and installation on the uncertainty in the energy calculation is presented. In addition, the affects of the transient behavior inherent in the cooling coil with respect to the energy balance was evaluated. This study gives insight to how an energy balance test coupled with an uncertainty analysis could be used to verify the cooling coil system performance and instrumentation output. Experimental results showed that the transient behavior inherent to the cooling coil had a negligible affect on the energy balance calculations and that by employing high accuracy instrumentation and careful installation, expected energy balance results could be attained. [ABSTRACT FROM AUTHOR]

The objective of the current investigation was to evaluate the field performance of a forced-air cooling system in an energy-efficient home. The test site was a three-story home in Pittsburgh, Pennsylvania, and field measurements were made during the cooling season. The forced-air system was zoned by floor and operated in both a zoned mode and in a non-zoned mode. The system performance was evaluated based on air temperature measurements and space conditioning energy use. The room air temperatures were compared to the requirements of ASHRAE Standard 55 (ASHRAE 2004b) for thermal comfort and recommendations of ACCA Manual D (ACCA 1995) for uniform temperatures between rooms. In non-zoned mode, the temperatures on the second and third floors exceeded the setpoint. Zoned operation improved the system temperature control performance, providing temperatures on the first and third floors that satisfied the ASHRAE and ACCA requirements. Temperature control for the second floor was not acceptable because of three problems: false thermostat temperatures due to air leakage, heat gain to uninsulated supply ducts in partially conditioned attic space, and solar load diversity. The zoning control increased the energy use per cooling degree-hour by approximately 6%; however this was not considered to be a significant variation due to the limited evaluation period. One conclusion of the study is that heat gain to ducts in conditioned (or partially conditioned) space can significantly impact the delivered cooling capacity to rooms. A preliminary conclusion from the investigation is that a zoned forced-air system can provide acceptable temperature control during cooling operation in an energy-efficient home. Additional research is recommended to investigate the impact of correcting the problems associated with Zone 2 (thermostat temperature issue and ducts in the attic space). [ABSTRACT FROM AUTHOR]

This paper presents a new methodology for the dynamic modeling of multi-evaporator air-conditioning cycles. The resulting model is suitable for designing advanced closed-loop controllers for these systems. A generalized modeling approach is developed, which is applicable to commercially available units with any number of evaporators. Model validation against data from an experimental dual-evaporator system for step inputs to compressor speed and expansion valve opening is also presented, and the results show good prediction accuracy The open-loop behavior observed in these simulation studies clearly indicates the effect of cross- coupling between dynamic variables of different evaporators. Finally, closed-loop control strategies based on the model and the system characteristics are discussed, and comparison of two control strategies for control of pressure and superheat of the two evaporators is also presented. [ABSTRACT FROM AUTHOR]