Energy-saving Design Of Constant Temperature And Humidity Air-Conditioning System And Optimization Of Chilled Water Temperature

With the development of industrial technology, as a kind of technical air-conditioning, constant temperature and humidity air-conditioning system has been widely used in the situations where air temperature and humidity is highly requested, such as, electronics industry, instrumentation equipment, medical treatment, precise workshop, computer room cooling. In the conventional constant temperature and humidity air-conditioning unit, air is cooled down and dehumidified by controlling method of the fixed chilled water flow rate and fixed dew point, then, electrical heating and electricity humidifying are used for thermal and humidity compensation, which will lead to great energy consumption. This text is based on the actual project to design a constant temperature and humidity air-conditioning system. The main contributions are listed as follow:1. Based on the review and analysis of current situation of energy saving in air-conditioning systems, This thesis designed and built a constant temperature and humidity air-conditioning system for a library treasury. Two kinds of energy saving measures are mainly used in the system:a set of temperature and humidity independent control device is added in coil-cooling, which consists of two electric three-way valves, two ordinary three-way valves and circulating pump. Meanwhile, the PID split-range control method is used to control two electric three-way valves and the input power of heater and humidifier, therefore, the purpose to precisely control temperature and humidity is achieved; stepping temperature method is adopted to control the eight compressors of the chiller, which can not only effectively reduce the overshoot of chilled water temperature to keep the system stable, but also effectively reduce energy consumption. A detailed design calculations and equipment selections is carried out for air system and water system of the constant temperature and humidity air-conditioning in this text.2. A set of automatic control software platform is compiled, which could match the hardware equipment very well. The system running test has proved the reliability of the software and the interface of the software is friendly with perfect function.3. After the design and construction of the system, in order to make the system more energy-efficient, TRNSYS software is employed to build model for the system. And then, experiment is adopted to verify the built model. Then on the basis of the established model, each month meteorological parameter of Hangzhou is called to optimize the chilled water setting temperature of the system in a variety of outdoor conditions. The simulation results show that:the energy-saving effect is obvious under the optimal set temperatures. In March, the energy efficiency is35.7%which is best of the year, the annual average energy efficiency is23.6%. The simulation results have practical significance for the guidance to system running.