Advanced Materials Research Vols. 516-517

Abstract: Entropy analysis method was adopted to analyze and optimize a jacketed pipes-type heat pipe steam generator. In the entropy analysis process, the entropy production resulted from the total temperature difference across the heat exchanger, the entropy production from main heat transfer element – heat pipes and the entropy production caused by the pressure drop due to working media flow on cold and hot sides were taken into consideration. In the calculation, the entropy production in all parts of the heat exchanger was analyzed row by row in a discrete pattern, except for the entropy production due to pressure drop on flue gas side. Analysis results show that for the heat exchanger in this case, the proportions of entropy production in the above-mentioned three parts are respectively 74.79%, 21.75% and 3.46%. On this basis, the article also made optimizing analysis with the cold and hot source temperature, heat pipe length and No. of heat pipe rows as parameters, to provide theoretical basis for further improving the energy efficiency of heat exchangers.

Abstract: Under four different working conditions (the smallest air door αpy =1.20,the smaller air door αpy =1.60, the larger air door αpy=2.30 and the largest air door αpy=3.50), the Peanut shell molding fuel Hot-blast Stove designed by the author have been tested. The corresponding result showed that the temperature distribution had similar rules in height, depth and width. The more reasonable and economical operations of the Peanut shell molding fuel Hot-blast Stove have been realized under the working condition 2 and 3. Their combustion efficiency of the boiler can reach 84.95％-92.07％and the thermal efficiency can reach 46.68％-56.73％. They have provided an effective way to solve the problem of heating in rural areas.

Abstract: This paper describes a designed new nozzle and provides experimental studies on the nozzle used in high-pressure fog cooling system in Greenhouses. Fogging droplet sizes of the nozzle is measured by MPA Malvern Particle Analyzer. The diameter of droplet sizes (VMD, Dv10, Dv50, Dv90) which is 500 mm far from the nozzle is measured and analyzed when the pump pressure is 2, 3, 4, 5, 6,7MPa.The experimental results shows: the nozzle has fine fogging performance, and its droplet sizes (VMD) are small and less than 30 microns when operating pressure is more than 5MPa.

Abstract: Many large capacity boilers are facing the problems of desulfurization with the variation of coal quality received and small designed desulfurization capacity in current Wet Flue Gas Desulfurization(WFGD) system. WFGD capacity improving renovation is a high cost and long construction cycle project. Therefore, a proposal to add accessorial limestone injection desulfurization system without changing the current WFGD was investigated in this study. Laboratory experiments and pilot scale field tests on a 220t/h boiler were performed to certificate the possibility of adding accessorial limestone desulfurization system on large capacity boiler. Desulfurization efficiencies under different injection position, Ca/S ratio, the porosity structures of desulfurization agent, and boiler operating conditions were tested to obtain the optimal working conditions for limestone desulfurization in large capacity boiler ; Ash composition, ash melting point, ash particle size distribution were also determined to evaluate the influence on heating surface of boiler corrosion, fouling, abrasion and boiler efficiency on a 660MW unit boiler after adding limestone injection system for security and economy concern. The results of this paper could provide reliable evidence and experiments data for the power plant to make overall consideration for adding accessorial limestone injection desulfurization system without changing the current WFGD system.

Abstract: As an application technology of renewable energy resource, water source heat pump (WSHP) has been paid more attention on. WSHP have been practiced especially for saving building energy consumption in Chongqing of China since there is abound water resources. However, it was found that some systems were not operated very well without achieving expected energy efficiency. Taking three real projects which use WSHP for heating and cooling of buildings in Chongqing city to test in field, key parameters were measured and operation performances were analyzed. The influences of water temperature and partial load ratio on system energy efficiency were studied. Based on existing problems, strategies for improving system energy performance are suggested from aspects of design and operating. Dynamic load hourly simulation plays a key role to determine appropriately the size and the form of system. More efforts have to be put on water pumps arrangement to save energy consumed for water transportation which accounts for large part of system energy. The temperature difference and water quality of water source should be controlled according actual operating conditions. The integrated systems and operation strategies under partial load are also beneficial for efficiency improvement.

Abstract: In this study, a study on heat transfer is performed for water upward flow in small channels to provide a systematic database for low pressure and mass flow velocity conditions. An empirical correlation on heat transfer in small channels for predicting the average Nusselt number has been derived by using Genetic Algorithm (GA).

Abstract: This paper has formulated a heat transfer model for analyzing the cooling properties of a heat pipe cooling device of oil-immersed electrical transformer. Based on the model, the oil temperature field of a 30 KVA oil-immersed transformer has been numerical simulated, and experiments also had been conducted. Results showed that the numerical simulation has good agreement with experiment results. Results also showed that heat pipe radiator is feasible for oil-immersed electrical transformer cooling. The model can be used to analyze the oil temperature distribution properties in an oil-immersed electrical transformer with heat pipe cooling device, and provide theoretical guide for transformer design and improvement.

Abstract: According to the application conditions of horizontal ground heat exchanger(HGHE) under artificial lake, this paper uses numerical simulation method to do dynamic simulation research of the heat transfer performance of HGHE, analyzes the effect of connection mode and pipe flow velocity on heat transfer performance of HGHE in detail，puts forward efficient HGHE loop formation mode，and will provide effective technical support for ground-source heat pump system design with HGHE.

Abstract: A heat radiation equation contains 4th exponential order of temperature which makes mathematics analysis complicated and time-consumption. Most heat transfer experts and scholars believe, based on their own experiences, that the heat radiation effect can be ignored in situations of small temperature difference between duct surfaces and surroundings. This paper studies in detail for complete heat transfer characteristics of a circular duct with heat radiation effect taken into account. It is found that, in some practical conditions, the heat radiation effect can not be ignored especially in cases of lower ambient convection heat coefficients and larger surface emissivities, as well as the smaller the duct size and/or the greater the duct conductivity and/or internal fluid convection coefficients, even though the temperature-difference between inner and outer fluid-temperatures of duct is low to 1 °C. It is found that the conventional LMTD method (ignoring heat radiation) cannot be applied to calculate the total heat transfer rate of a single-duct heat exchanger located in ambient air, such as condenser and evaporator.

Abstract: The level of domestic gas utensils energy utilization efficiency decides the energy saving efficiency and economical efficiency of the gas utensils. In this paper, considering the stove-cooking utensil as the object of study, on the basis of deep research of stove-cooking utensil system’s high-effective heat transfer, high-effective heat preservation technology, combing the technology of high-effective burning, high-effective heat transfer, high-effective heat preservation, a stove-cooking utensil system that is of high-effective heat transfer, high-effective heat preservation, low cost, low exit flue gas temperature is designed and the stove-cooking utensil system’s energy efficiency is improved significantly by comprehensive designing and researching of the insulation lid, the bottom of pot, and the radiant panel on the condition of keeping high-effective burning.