Jingxiao Han¹, Chuanzhao Zhang², Lu Wang^3,*, Zengjun Chang¹, Qing Zhao¹, Ying Shi⁴, Jiarui Wu⁵, Xiangfei Kong³

Energy Engineering, Vol.120, No.9, pp. 1991-2011, 2023, DOI:10.32604/ee.2023.029749

Abstract For heating systems based on electricity storage coupled with solar energy and an air source heat pump (ECSA), choosing the appropriate combination of heat sources according to local conditions is the key to improving economic efficiency. In this paper, four cities in three climatic regions in China were selected, namely Nanjing in the hot summer and cold winter region, Tianjin in the cold region, Shenyang and Harbin in the severe cold winter region. The levelized cost of heat (LCOH) was used as the economic evaluation index, and the energy consumption and emissions of different pollutants were analyzed. TRNSYS software was… More > Graphic Abstract

Huashan Li¹, Xiaoshuang Zhao^1,2, Sihao Huang^1,2, Lingbao Wang¹, Jiongcong Chen^1,*

Energy Engineering, Vol.120, No.8, pp. 1817-1835, 2023, DOI:10.32604/ee.2023.027668

Abstract Process heating constitutes a significant share of final energy consumption in the industrial sector around the world. In this paper, a high-temperature heat pump (HTHP) using flash tank vapor injection technology (FTVI) is proposed to develop low-temperature geothermal source for industrial process heating with temperature above 100°C. With heat sink output temperatures between 120°C and 150°C, the thermo-economic performance of the FTVI HTHP system using R1234ze(Z) as refrigerant is analyzed and also compared to the single-stage vapor compression (SSVC) system by employing the developed mathematical model. The coefficient of performance (COP), exergy efficiency (η_exe), net present value (NPV) and payback… More >

Yuqin Wang^1,2,3,*, Luxiang Zhou³, Mengle Han¹, Lixiang Shen¹

FDMP-Fluid Dynamics & Materials Processing, Vol.19, No.9, pp. 2215-2228, 2023, DOI:10.32604/fdmp.2023.027188

Abstract The main structural parameters of the IR100-80-100A type chemical centrifugal pump have been optimized by means of an orthogonal test approach. The centrifugal pump has been modeled using the CFturbo software, and 16 sets of orthogonal-test schemes have been defined on the basis of 4 parameters, namely, the blade number, blade outlet angle, impeller outlet diameter, and impeller outlet width. Such analysis has been used to determine the influence of each index parameter on the pump working efficiency and identify a set of optimal combinations of such parameters. The internal flow field in the centrifugal pump has been simulated by… More > Graphic Abstract

Yan Chen^a , Qingxin Ba^b,*, Xuefang Li^b

Frontiers in Heat and Mass Transfer, Vol.16, pp. 1-9, 2021, DOI:10.5098/hmt.16.18

Abstract The heat transfer of supercritical CO₂/DME mixtures was modeled in this study for a mass ratio of 95/5 for cooling in horizontal helically coiled tubes. The CO₂/DME heat transfer coefficient was higher in the high-temperature zone than with pure CO₂. The heat transfer of CO₂/DME (95/5) was predicted for various mass fluxes, heat fluxes and pressures. The CO₂/DME heat transfer coefficient increased with the mass flux due to the increased turbulent diffusion, and first increased but then decreased with the heat flux. The peak heat transfer coefficient of CO₂/DME shifted toward the high-temperature region as the operating pressure increased. The… More >

V. W. Bhatkar^a,*, Anirban Sur^b,*

Frontiers in Heat and Mass Transfer, Vol.17, pp. 1-5, 2021, DOI:10.5098/hmt.17.12

Abstract A jet pump or an ejector uses primary fluid flow as motive fluid to entrained secondary fluid. In this paper, the main intention is to find suction flow rate, primary flow rate, secondary flow rate, loss factors and ejector efficiency for an applied pressure. The values of the different loss factors estimated are primary nozzle loss factor (Kp)=0.06, suction loss factor (Ks)=0.04-0.1, mixing loss factor (Km)=0.07-0.1 and diffuser loss factor (Kd)=0.0289. It is found that with the increase in pressure across the ejector, efficiency increases with increase in flow ratio and decrease in pressure ratio. More >

Xiao Sun^a, Fan-Kang Zeng^a, Jia-Bing Yang^a, Feng-Lin Zhou^a, Yu-Liang Zhang^b,*

Frontiers in Heat and Mass Transfer, Vol.17, pp. 1-6, 2021, DOI:10.5098/hmt.17.5

Abstract In order to better study the internal flow characteristics of centrifugal pump as turbine, CFX software is employed to carry out numerical simulation to obtain flow field under different working conditions for pump as turbine based on the standard k - epsilon turbulence model and the SIMPLEC algorithm. The efficiency curves of the pump and pump as turbine are obtained under different working conditions. The results show that the effciency characteristics of the pump change greatly during the process of pumping. The efficiency of the turbine is higher than that of the pump under the respective optimal operating conditions. The… More >

Y. L. Zhang^a , H. B. Lin^b, S. P. Li^b,*, J. J. Xiao^a, L. Zhang^c

Frontiers in Heat and Mass Transfer, Vol.18, pp. 1-6, 2022, DOI:10.5098/hmt.18.47

Abstract Centrifugal pumps need to be stopped in the case of closing valve sometimes due to some specific application requirements. This paper presents a numerical simulation of the unsteady flow inside a low specific speed centrifugal pump during closed-valve forward and reverse stopping process. The study results show that the average internal pressure gradually decreases during stopping periods. At the same blade radius, the pressure on working surface is significantly higher than the suction surface. The pressure gradually increases from the impeller inlet to the outlet. The simulation fully shows the transient flow characteristics inside the centrifugal pump during forward and… More >

Le Anh Duc^a , Nguyen Hay^a, Pham Van Kien^b,*

Frontiers in Heat and Mass Transfer, Vol.18, pp. 1-7, 2022, DOI:10.5098/hmt.18.44

Abstract This study determined the most appropriate thin layer drying model, the effective moisture diffusivity and the activation energy of moisture within Ganoderma lucidum in radio frequency (RF) assisted heat pump drying method. The thin layer drying experiments were conducted with input drying parameters such as: drying temperature of 40, 45 and 50°C and RF power of 0.65, 1.3 and 1.95 kW. In order to select a suitable form of drying curve, seven different thin layer drying models (Lewis, Page, Modified Page, Henderson and Pabis, Verma, Midilli, and Wang and Singh) were fitted to the experimental data. The Verma model was… More >

L. Cheng, Y. L. Zhang^†

Frontiers in Heat and Mass Transfer, Vol.18, pp. 1-6, 2022, DOI:10.5098/hmt.18.26

Abstract To obtain the transient characteristics of a centrifugal pump during a rapid startup process accurately, a circulating piping system, including the pump, is established. A full three-dimensional unsteady incompressible viscous flow of a low-specific speed centrifugal pump during rapid startup is numerically simulated using the finite volume method, RNG k-ε turbulence model, sliding grid technology, dynamic grid technology, and userdefined function. Results show that the effect of dynamic and static interference becomes remarkably evident with the increase in speed in the starting process. The effect of dynamic and static interference makes the flow rate show small fluctuation characteristics, and the… More >

L. Cheng^a , Y. L. Zhang^a,† , J. F. Li^b

Frontiers in Heat and Mass Transfer, Vol.19, pp. 1-7, 2022, DOI:10.5098/hmt.19.32

Abstract The internal characteristics during rotational speed fluctuation have an important influence on centrifugal pump to avoid or utilize its transient performance. In this paper, a circulation piping system that includes a low-specific-speed centrifugal pump is established to study the energy distribution characteristics in a centrifugal pump during speed fluctuation. The unsteady flow in the entire system is numerically calculated with a user-defined function, the sliding grid method, and the RNG k-ε turbulence model. Then, the energy distribution of the transient flow field in the centrifugal pump model during speed fluctuation is diagnosed with vortex dynamics by using flow section and… More >