We present the dynamic modelling of an absorption system and an application to a large air-conditioned system. This study was performed using the ALLAN.Simulation software, a pre- and post- processor enabling the symbolic description of systems. The absorption system is a direct gas double effect absorption chiller or heater, using LiBr/HB2BO as working fluid. This modelling has two aims. The first one is to optimize the water circuit by determining the volume of a storage tank that maximise the energetical and economic operation performances.
An experimental setup of a water based central heating system has been used to measure the thermo dynamical behavior of a thermostatic valve in order to identify an adequate mathematical model. The identification of the thermostatic valve is based on nonlinear Grey-Box modelling. Grey-Box modelling is characterized by the fact that, in the modelling procedure, partial known information from physics about a system is combined with information from data. The parameters of the model are estimated by a Maximum Likelihood Method. In the paper an overview of this modelling procedure is given.
Cooling towers are often used in air conditioning applications to reject heat into the atmosphere. For many people in the industry, the thermal performance of cooling towers is often taken for granted. With proper control of condenser water temperature from the cooling tower, up to a 27% increase in efficiency of a central chilled water plant can be realized. The condenser water system for a chilled water plant usually consists of three major components: water chillers, cooling towers and circulating water pumps.
Refrigerated display cases are normally rated at a store environment of 24P0PC (75P0PF) and a relative humidity of 55%. If the store can be maintained at lower relative humidities, significant quantities of compressor energy, defrost energy and anti-condensation heater energy can be saved. In this study a model was developed for a 4650 mP2P (50,000 ftP2P) food store with a typical mix and quantity of refrigerated display cases. Moisture balances were done for a typical day in a typical store for each month of the year yielding a twenty-four hour variation in the store relative humidity.
Space conditioning of a laboratory environment is more complicated than that of a typical commercial office building space. Safety considerations impose additional constraints over the usual comfort requirements. The control actions required to provide safety often counteracts those needed to meet comfort criteria. The dynamic interaction between the different control systems is complex and critical to laboratory safety. A description of a dynamic simulator for use in design and evaluation of laboratory HVAC systems is presented in this paper.
This work focuses on the testing and modelling of a bisplit refrigeration system. This system is composed of two evaporating circuits (each circuit consists of an expansion device and an evaporator) connected in parallel inside the same refrigeration unit. The test bench developed in the Laboratory of Thermodynamics is briefly described and the influence of the refrigerant charge effect on the system global performance is examined. The modelling of a bisplit chiller is also studied and a first model validation is given.
Energy requirements for HVAC systems operation in buildings must be known on account of the necessity to determine the operation costs of the buildings and to carry out analyses aimed at improvement of design conceptions applied in buildings and installations as well as their operational parameters. It is commonly assumed that the most useful tool for such analyses is a detailed simulation model: building HVAC system. However, the number of details included in the model makes the analyses very labour demanding and may result errors when preparing simulation data.
This paper presents two approaches used to develop a model of Room Storage Heater. The first one consists of a dynamic model of the RSH developed by the authors using the results obtained from tests performed in a calorimetric chamber. The model was verified against the results obtained during five different charge-discharge test periods. The second approach is a new concept based on Neural Networks applications. In this approach, we suppose that we do not have a description of the RSH itself.
The authors have created a Neural-Fuzzy Assistant which acts as a Decision Support System and helps to perform quickly and easily the estimations of office building energy consumption. The Neural-Fuzzy Assistant presented in this paper allows the user to determine the impact of eleven building parameters on the electrical annual and monthly energy consumption, annual and monthly maximum electrical demand and cooling and heating annual consumption and demand.
In order to reduce the energy demand in the field of heating, ventilation and air conditioning many efforts have been made during the last decades. HVAC-components used nowadays are much more advanced than those used years ago. The success of the energy saving endeavors becomes even more apparent if the controlling devices, and there especially the implementable controlling strategies, are put in the center of view. In former times the controlling appliances in HVAC-systems consisted of analog devices which were relatively inflexible in regard to varying controlling strategies.
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