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The scaling of high pressure heat exchanger between feedstock and reaction effluent in residue hydrogenation unit of J Petrochemical Company caused the decrease of heat exchange efficiency, which directly affected the stable operation and benefits of the unit. Through comparison with similar domestic units, it was found that the selection of medium in the shell and tube side of high pressure heat exchanger and the flow rate of fluid had a great impact on the scaling of high pressure heat exchanger. Based on the operation experience of similar units, the proposed measures to improve the scaling of high pressure heat exchanger were put forward. On the one hand, the feedstock properties and hydrogen-to-oil ratio during the operation of the unit were well controlled to slow down the scaling tendency of high pressure heat exchanger. On the other hand, by adding a high pressure heat exchanger, exchanging the medium of the shell and tube side, and optimizing the design of the heat exchanger, the heat exchange efficiency of the heat exchanger was fundamentally improved. [ABSTRACT FROM AUTHOR]

In order to meet the requirments of GB 31570-2015 Emission Standard for Pollutants in Petroleum Refining Industry, and improve regional environmental quality, the desulfurization technology widely used in catalytic flue gas has been modified adaptively, the gas-gas heat exchanger and high efficiency demister has been added, and the Venturi desulfurization technology（SVDS） suitable for sulfur recovery unit has been formed. The Venturi desulfurization technology was applied in sulfur recovery unit of Dushanzi Petrochemical Company. After transformation, the SO2 mass concentration in flue gas reduced from 300 mg/m³ to less than 30 mg/m³, which met the requirements of GB 31570-2015 about SO2 mass concentration emission limit in special emission limit areas. During the operation process of Venturi desulfurization technology, some problems such as the pressure drop of gas-gas heat exchanger raised and corrosion of pump casing and impeller of lye pump occurred successively. Corresponding measures were formulated to ensure the long period operation of alkaline cleaning facilities. [ABSTRACT FROM AUTHOR]

Tibetan medicine has a long history to serve as a national medicine second only to Chinese medicine. Fresh Tibetan medicine cannot be directly used as medicine. Drying process is essential as a preliminary processing step. The heat pump drying method can be suitable for this case, due to its energy saving, environmental protection, and low cost. In this study, a novel drying system mode of heat recovery and air-jet enthalpy heat pump was proposed to improve the drying characteristics of Tibetan medicine under low-temperature environments. A systematic experiment was conducted to explore the stability and energy efficiency for the continuous operation of system, thereby to obtain the changing characteristics of continuous operation on the heat pump in different load modes at low temperature conditions. In order to explore the performance characteristics of heat pump drying for the Tibetan medicine at low temperature environment in winter, a drying oven was built with the size of 3.9m ×2.1m ×2.3m (length ×width ×height)and a volume of about 15m³, as well as a rated load of 1.5 t. An ordinary ring scroll compressor,and an air jet enthalpy compressor in a heat pump system were selected to carry out the load experiment test at the ambient temperature of -11.4−18.3 and -13.39−16.69°C. The ordinary scroll compressor in a heat pump system worked in the segmented drying mode, and the continuous drying operation mode was used to dry Tibetan medicine. The air-jet enthalpy-increasing heat pump system performedday and night for the continuous drying. Results were as follows: Under the severe cold and large temperature difference (30°C) in the winter plateau, the average efficiencyof heat transfer in the air-jet enthalpy-increasing heat pump system (-13.39−16.69°C) was 9.56%, and that in the ordinary scroll compressor heat pump system (-11.88−18.29°C) was 13.58%. It infers that the efficiency of heat transfer in a heat exchanger was relatively low, as the ambient temperature decreased.The compressor selection has no significant effect on the heat exchange efficiency of heat exchanger. The minimum coefficient of performance (COP) of air-jet enthalpy-increasing heat pump system(-13.39−16.69 ℃) increased by 51.5%, compared with the ordinary scroll heat pump system (-11.4−18.3 ℃). The average value of COP increased by 16.9% during the whole progress, indicating effectively improved the heating energy efficiency of a system at low temperatures. The placement and thickness of amaterial presented a significant influence on the drying effect. When the loading capacity of drying box was about 100% and stacking thickness was 20 cm, the final product behaved bright color, uniform drying, and the high specific moisture extraction rates (SMER). Compared with the traditional air-drying method, the drying time of a heat pump was only 1/9 of conventional dry method for the same amount of materials, while,the drying cost was reduced by 1 160 yuan/t. The recovery and air-jet enthalpy heat pump system can meet the energy supply that required for the drying of Tibetan medicinal materials under the low-temperature conditions. [ABSTRACT FROM AUTHOR]

Microchannel heat exchanger is highly efficient in heat exchange due to its microscopic structure and large heat exchange surface area ratio. Compared with conventional heat exchanger, it not only improves heat exchange efficiency but also saves space and reduces the weight of heat dissipation equipment. In agriculture, microchannel heat dissipation technology has been widely used in cultivation, machinery, and product drying. Microchannel increases resistance to fluid flow and could thus result in an increase in energy consumption. It could also give rise to a pressure-drop oscillation affecting operation of the system. Previous work showed that electric field has a beneficial impact on heat transfer efficiency in the microchannel heat exchanger. The purpose of this paper is to investigate how different electrodes (needle type and linear types) affect pressure drop of the boiling R141b coolant when it flows in the microchannel. The pressure in the system was kept at 140 kPa, the working inlet temperature was 32.5, the mass flow rate ranged from 277.35 ℃ to 531.75 kg/(m²·s), the heat flux density ranged from 7.50 to 21.49 kW/m², the voltage ranged from 0 to 850 V, and the microchannel was rectangular with a cross section of 2 mm×2 mm. The results showed that the electric field under both electrodes increased the frictional pressure drop in the microchannel, compared with that without electric field. The frictional pressure drop of the two-phase along per unit length increased with both voltage and heat flux. The average two-phase frictional pressure drop along per unit length under the needle and the linear electrode was increased 0.7% to 15.4% and 1.3% to 18.7%, respectively, that without electric field. When the voltage changed from 0 to 250 V, the effect of the needle electrode on the pressure drop was greater than that of the linear electrode, while when the voltage was higher than 400 V, the effect of the linear electrode on the pressure drop was more significant. We simulated the electric field distribution in a microchannel 6 mm long using COMSOL for both electrodes. The results showed that under the same voltage, the maximum of the electric field intensity in the needle electrode was higher than that in the linear electrode, but the effective range of the electric field in the linear electrode was higher than that in the needle electrode. The results presented in this paper provide an alternative to improve performance of microchannel heat exchanger and reduce its energy consumption. [ABSTRACT FROM AUTHOR]

Aiming at the demand of aeroengine thermal management system，this paper proposes a regular octahedral porous structure heat exchanger and studies its internal flow and heat transfer characteristics. The study find that the regular octahedral porous structure can effectively improve the heat exchanger efficiency， but with the decrease of Ce，the flow resistance outside the pipe will increase rapidly. When the Ce decreases to 10，the coefficient of resistance outside the tube increases to 18.2 times as much as that of the light pipe. Therefore，the internal structure optimization of the heat exchanger is carried out. In the case of improving the internal heat transfer，the internal flow resistance is reduced as much as possible，thus obtaining the optimal heat transfer resistance comprehensive coefficient Ce. [ABSTRACT FROM AUTHOR]