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This study investigated the effect of an energy saving device (ESD) on the performance of a split-type air conditioner (SAC). The ESD was fabricated using a moisture-transferring and quick-drying textile (MTQDT), a condensate pipeline, and a distributor. The MTQDT was coated on the shell surface of the compressor to absorb the condensate expelled by a condensate pipeline and distributor to enable evaporative cooling of the compressor. The SAC was tested under various outdoor air conditions (29, 32, and 37   °C; 55% relative humidity) and under a fixed indoor air condition (26   °C; 50% relative humidity), and the performance of the SAC before and after ESD installation was compared. Results demonstrated that the MTQDT effectively improved compressor cooling and the efficiency of the SAC. Compared with the SAC without an ESD under the optimal condition, the shell temperature of the compressor, high-side pressure, and power consumption of the proposed SAC were 15.1   °C, 2.7%, and 9.2% lower, respectively. Moreover, the dehumidification capacity and energy efficiency ratio of the proposed SAC were 25.4% and 7.3% higher, respectively. [ABSTRACT FROM AUTHOR]

When receiving an urgent request from a smart grid, shutting down part of operating chillers directly in the air-conditioning system in a building can achieve immediate power reduction. However, no study has addressed how to determine the number of chillers/pumps to be shut down and how to regulate the load of retained equipment systematically during DR events. This paper presents a new approach to address these issues based on three schemes. A power demand optimization scheme predicts the building cooling demand and the power limiting threshold in response to a received DR request. A system sequence control resetting scheme determines the number of operating chillers/pumps to be retained. An online control/regulation scheme ensures the system power following the expected profile by regulating the total chilled water flow delivered to the building and therefore the chiller load. It also employs a cooling distributor to distribute chilled water to individual zones concerning different sensitivities/sacrifices to temperature increases. Case studies are conducted on a simulated dynamic building air-conditioning system. Results show that, during DR events, the proposed strategy can achieve the expected power reduction (i.e., about 23%) and also maintain acceptable zone temperature even though uncertainties exist in the prediction process. [ABSTRACT FROM AUTHOR]

The degree of jet entrainment is affected by the exit conditions and thus affect the air terminal device design. While investigations of jet exit conditions have been carried out by experiments and simulations, it can be considerable advanced by the theoretical analysis. Effect of velocity profile and turbulence intensity at jet exit on jet entrainment are examined based on the field synergy theory by calculating the mass transfer field synergy number, that is the synergy between the velocity vectors and the species concentration gradients for a given jet flow rate. It showed that the entrainment increases with the increase of the mass transfer field synergy number, and vice versa. The mass transfer field synergy number can be changed by the boundary conditions to strengthen or weaken the convective mass transfer of jet entrainment. This work has resulted in a better understanding of the convective mass transfer phenomenon of jet entrainment and give a guide for air terminal device design. [ABSTRACT FROM AUTHOR]

A thorough assessment is critical for understating and enhancing building energy performance. This paper presents a three-level energy performance assessment method for information-poor buildings where very limited energy use data are available. Using this method, the energy performance of a building can be assessed at multiple levels (i.e., building level, system level and component level ) based on limited energy use data and few in-situ measurement and/or catalogue data of air-conditioning systems. The core part of this assessment method is a quantitative energy performance calculation method that consists of two basic energy balances, simplified models of air-conditioning components and an optimization algorithm based on the energy balances within buildings. The proposed assessment method is well validated in a high-rise building in Hong Kong by comparing the energy performance data from the proposed method with that from detailed measurements. Results show that this method can estimate the energy performance indicators quantitatively at three levels with acceptable accuracy. [ABSTRACT FROM AUTHOR]

In this paper, we present the application of neuro-fuzzy system-ANFIS for air conditioning systems to reduce electricity consumption. The current buildings have automation systems that provide data on lighting, electrical system, air conditioning system, etc. We studied the air conditioning system, in particular, to reduce energy consumption as air conditioning has a high consumption value. Our main goal in this study is the application of neuro-fuzzy system-ANFIS with the adjustment of the rules made by a decision tree-CART algorithm in air conditioning system. We compared the results of the application of the ANFIS-CART system with the application of PID controllers and fuzzy control system for a central air conditioning. [ABSTRACT FROM AUTHOR]

Control of air-conditioner units is essential to achieve satisfactory comfort conditions in buildings while keeping low energy consumption and operation costs. In this paper, a nonlinear multiinput & multioutput model (MIMO) of an air-handling unit (AHU) is considered. After linearization of the state equations around the operating points, an observer and a regulator are designed for the estimation of state variables and disturbance rejection, respectively. A realistic uncertain model is considered which constitutes various uncertainties associated with complex nonlinear model of AHU. In the presence of model uncertainties, a H ∞-robust controller is designed to guarantee robust performance of the air-handling unit. In addition, a simple controller based on pole-placement approach is developed. Indoor temperature and relative humidity are controlled via manipulation of valve positions of air and cold water flow rates. Achievement of tracking objectives is investigated through various desired commands of indoor temperature and relative humidity (including a sequence of steps and ramps-steps). According to results, the H ∞-robust controller guarantees the robust performance of the AHU in tracking of desired set-paths (while using the simple pole-placement controller leads to high oscillatory behavior of the output variables and control efforts). Moreover, using H ∞-robust controller results in less energy consumption in comparison with the pole-placement controller. [Copyright &y& Elsevier]

Abstract: In this paper, a control framework for the air-conditioning system operated in heating mode is proposed. The control framework possesses a cascade structure for dealing with the fast and slow dynamics respectively contributed by the vapor compression cycle and the indoor dynamics. Under the control framework, the control performances associated with two strategies, the condenser superheat regulation (CSR) strategy and the evaporator superheat regulation (ESR) strategy are examined. It is shown experimentally that while ESR strategy demonstrates more superior transient response, CSR strategy is more advantageous in reducing the compressor power at steady state. In order to achieve both transient performance and steady-state power savings, the two strategies are combined in the way that ESR strategy is responsible for the control action during the startup/transient phase of operation, CSR strategy takes over the control when steady state is reached, and a bumpless compensator is used to smooth the control action during control switching. Experiments demonstrate that the combined strategy can simultaneously enhance transient performance and steady-state efficiency. [Copyright &y& Elsevier]