Syeda Humaira Tasnim^a,*, Shohel Mahmud^b, Roydon Andrew Fraser^a

Frontiers in Heat and Mass Transfer, Vol.2, No.1, pp. 1-10, 2011, DOI:10.5098/hmt.v2.1.3006

Abstract In this paper, we experimentally measure the temperature fields at different locations on the stack plate and in the surrounding working fluid in a standing wave thermoacoustic device. The temperature measurements at the stack extremities and at the neighboring gas show axial heat transfer at the stack extremities, as opposed to the hypothesis of a perfectly isolated stack used in the linear thermoacoustic theory. Four different mechanisms of heat transfer are identified at the stack extremities in the present study. This information is necessary for the optimization of the performances of practical thermoacoustic engines. For the selected operating conditions, temperature… More >

Jiarui Wu¹, Yuzhen Kang², Junxiao Feng^1,*

Energy Engineering, Vol.120, No.12, pp. 2783-2802, 2023, DOI:10.32604/ee.2023.029358

Abstract To enhance system stability, solar collectors have been integrated with air-source heat pumps. This integration facilitates the concurrent utilization of solar and air as energy sources for the system, leading to an improvement in the system's heat generation coefficient, overall efficiency, and stability. In this study, we focus on a residential building located in Lhasa as the target for heating purposes. Initially, we simulate and analyze a solar-air source heat pump combined heating system. Subsequently, while ensuring the system meets user requirements, we examine the influence of solar collector installation angles and collector area on the performance of the solar-air… More >

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 >

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 >

Le Anh Duc^a , Pham Van Kien^b,*, Nguyen Thanh Tan^b, Doan Thanh Son^b, Nhanh Van Nguyen^c, Ngoc Xuan Nguyen^d

Frontiers in Heat and Mass Transfer, Vol.20, pp. 1-6, 2023, DOI:10.5098/hmt.20.25

Abstract This study focused on the heat and mass transfer in radio (RF) assisted heat pump (HP) drying of carrots. The experimental drying of carrot by RF assisted HP drying method was conducted to evaluate the effect of RF power on drying efficiency including drying rate and heating rate. The input drying parameters were drying air temperature of 45oC, drying air velocity of 2.5 m/s and RF power of 0, 0.5 and 1.5 kW, in which, RF power of 0 was corresponding to HP drying method. The experimental drying results showed that in RF assisted HP drying method, the drying rate… More >

Siwei Han^1,*, Xianglong Li², Wei Zhao¹, Linyu Wang¹, Anqi Liang², Shuang Zeng²

Energy Engineering, Vol.120, No.6, pp. 1421-1444, 2023, DOI:10.32604/ee.2023.027094

Abstract Photovoltaics, energy storage, direct current and flexibility (PEDF) are important pillars of achievement on the path to manufacturing nearly zero energy buildings (NZEBs). HVAC systems, which are an important part of public buildings, play a key role in adapting to PDEF systems. This research studied the basic principles and operational control strategies of a DC inverter heat pump using a DC distribution network with the aim of contributing to the development and application of small DC distribution systems. Along with the characteristics of a DC distribution network and different operating conditions, a DC inverter heat pump has the ability to… More >

Rabeb Toujani, Nahla Bouaziz^*

FDMP-Fluid Dynamics & Materials Processing, Vol.19, No.4, pp. 991-1001, 2023, DOI:10.32604/fdmp.2022.022239

Abstract A hybrid heat pump (compression/absorption) with an integrated thermal photovoltaic unit is studied. The considered working fluids are organic mixtures: R245fa/DMAC and R236fa/DMAC, chosen for their low Global Warming Potential. The main objective is the optimization of energy efficiency in order to minimize the environmental impact through the implementation of a sustainable strategy. It is shown that Exergy Analysis itself is a valuable tool in energy integration. Within the imposed framework of minimizing total annual costs, entropy analysis can be instrumental in determining the optimal plant concept, optimizing energy conversion and use, and improving profitability. The present results are discussed… More >

Ting Chen¹, Oh Kyung Kwon^2,*

Energy Engineering, Vol.119, No.6, pp. 2231-2242, 2022, DOI:10.32604/ee.2022.021289

Abstract With the limited production and use of R245fa, environmentally friendly refrigerant has attracted the attention of researchers. Due to the similar thermal characteristics, R1233zd(E) is considered to be an ideal substitute for R245fa in heat pump systems. In this study, the performance and economic analysis of heat pump systems with R245fa and R1233zd(E) as refrigerants are carried out. The results show that the total cost of R1233zd(E) system is more than 10% higher than that of R245fa system under the same heating load. With the increase of condensation temperature, the heating capacity of both systems decreases, and with the increase… More >

Ali H. Tarrad^*

FDMP-Fluid Dynamics & Materials Processing, Vol.18, No.4, pp. 1111-1127, 2022, DOI:10.32604/fdmp.2022.021541

Abstract An analytical model was built to predict the thermal resistance of a vertical double U-tube ground-coupled heat pump that operates under steady-state conditions. It included a geometry obstruction factor for heat transfer throughout the backfill medium due to the presence of the second loop. The verification of the model was achieved by the implementation of five different borehole configurations and a comparison with other correlations in the available literature. The model considered a U-tube spacing range between (2) and (4) times the U-tube outside diameter producing a geometry configuration factor range of (0.29–0.6). The results of the model were utilized… More >