Applied Mechanics and Materials Vols. 291-294

Abstract: Several indexes for evaluating the global warming impact, including GWP (global warming potential), TEWI (total equivalent warming impact) and LCCP (life cycle climate performance), are analyzed and investigated from the concept, contents, difference and correlation among them. LCCP is a rigorous method to calculate the cradle-to-grave warming impact of different refrigeration and air conditioning systems. The LCCP index was therein used to analyze overall greenhouse effect of three air conditioning cold and heat source plans for a public building. The results show that the total amount of equivalent CO2 emission from air conditioning heat and cold sources is up to 50,000 tons throughout the life cycle. Indirect global warming impact dominated the LCCP values of cold and heat source systems, which accounts for >96% of overall impact and caused by energy consumption both for producing refrigerant and operating refrigeration and air conditioning equipment. Therefore, increasing the energy efficiency of air conditioning and refrigeration equipment to reduce indirect global warming impact is the key to lowering A/C’ total impact on climate change. The LCCP of water source heat pump is always lower than that of conventional electric water chillers plus gas direct-fired unit, and its carbon emission reduction rates up to 32.4% as compared to the latter. So the overall impact from air conditioning cold and heat source could be effectively reduced through using renewable energy technology.

Abstract: The large building air conditoning system with different modes were made , which include the constant air volume system, variable air volume system, the temperature and humidity independent control system. To calculate energy saving rate, the energy consumption simulated by DeST energy simulation software.

Abstract: Load imbalance of power grid leads to more peak-load power station built with huge capital cost and some environment effects. As a peak shifting technology, thermal storage technology has attracted more attentions. A new operating mode of chilled storage process integrated with air-conditioning system is proposed, and its performance is analyzed. The results show that the new operating mode can get more than 5% of power saving than the traditional mode, and achieve more than 40% power cost saving based on air-conditioning without chilled storage, both of which result from the good integration of chilled storage process with air-conditioning system. The new operating mode gives the new direction of thermal storage technology application.

Abstract: This study aims to investigate energy saving efficiency of condensing heat recovery device installed in constant temperature/humidity system. In the experiment, heat tank (heat exchanger) firstly stores condensing heat, which replaces the role of electric reheating method in traditional constant temperature/humidity system. And then the study discusses the effect of reheating methods, electric heating and heat recovery, on temperature, relative humidity, and electricity consumption in the constant temperature/humidity system. The experimental result shows that the heat recovery device exerts better control on temperature and relative humidity under differential room loads. And by providing additional power dissipation for the water pump and the fan only, it meets the requirement of reheat supply. As a result, overall power consumption of the constant temperature/humidity system reduces by 22.5-38.2%. This study uses the reheat recycled through condensing heat recovery and supplied to the constant temperature/humidity air-conditioning equipment, and indeed reduces electricity consumption of the overall constant temperature/humidity system and maintains a stable temperature and humidity environment.

Abstract: To predict the performance of screw chillers in variable operating conditions, a steady state model of screw chillers suitable for variable conditions simulation was built and tested. Comparison between the predicted value and the experimental value shows good agreement. The results show that this model is suitable for variable inlet temperature and mass flow rate of chilling water and condensing water. Refrigerating capacity and condensing heat release condition of a specified screw chiller could be calculated if a set of outer thermal parameters is gained. This model is useful for simplifying performance test, equipment selection and running control.

Abstract: Oversized boilers in in-house heat stations are relatively common. This study demonstrates the effect of installed overcapacity in heat stations with regard to the buildings heat load. Potential energy savings are calculated on basis of a heat station containing both fuel oil boiler and electric boiler. Correct installed capacity is defined as the capacity of a boiler designed to meet the design outdoor temperature, DOT. The baseline for normal consumption has been defined by utilization of correct designed boilers operated under various climatic conditions for a normal year. This baseline has then been compared to consumption calculation done with oversized boiler capacity. The energy consumption calculation is done on an hourly basis for one year. The results show a clear connection between the boiler size, boiler efficiency and potential savings in energy and cost.

Abstract: This study demonstrates the effect on energy consumption and operational cost effect of oversized boilers. Potential energy and cost savings are calculated on basis of a heat station containing both fuel oil boiler and electric boiler. Correct installed capacity is defined as a boiler designed to meet the design outdoor temperature, DOT. The baseline for normal consumption is defined by utilization of both boilers. This baseline has then been compared to consumption and cost calculation done with over sized boiler capacity. The calculation is done on an hourly basis for one year. The results show a clear connection between the boiler size and potential savings in energy and cost.

Abstract: This paper presents a theoretical and experimental analysis of a pulse combustion in reheating furnace. Measurements of the composition content on flue gases and heat balance tests were carried out for operating parameters in reheating furnace. Experimental results show an intensive and efficient heating process. An attempt was made to perform theoretical computation of composition content in the reheating furnace. Satisfactory agreement between calculations and experimental results was found in certain regions. Discrepancies might be caused by sample of the combustion products which were assumed to be uniform distribution out of the reheating furnace. The results show that the pulse combustion has comparatively large influence upon both combustion and heat efficiency in a reheating furnace.

Abstract: Over-concentrated load added the generator start-stop frequency and energy consumption, being harmful to the generator running efficiently and economically, dignifying the security and stability of the electricity system. Based on the time-of-use(TOU) price mechanism, this paper suggests superstores take advantage of energy-storage equipment to transfer load and proposes a decision-making model of air-conditioning options. By comparing the costs of the ice-storage air-conditioning with the regular air-conditioning, we find the ice-storage air-conditioning shows much contribution to the power net stability, to energy saving and to the cost decreasing of the superstores.

Abstract: Whether the results of the dynamic heat flux from the underground engineering envelope are accurate, may influence the accuracy of calculating the transient heat load and could affect the initial cost and actual operation of the air-conditioning system in the underground engineering. The paper is to find out the mechanisms of the heat transfer in the underground engineering envelope. The mechanisms of heat transfer in normal underground engineering envelope, simplified calculation for heat transfer in the underground engineering envelope and the dynamic emulation of the heat load of the underground engineering envelope.