Begell House Inc.
Heat Transfer Research
HTR
1064-2285
51
14
2020
EXPERIMENTAL AND NUMERICAL STUDY OF THE CHARACTERISTICS OF FINNED-TUBE OIL RADIATORS OF POWER ENGINEERING DEVICES
1261-1271
10.1615/HeatTransRes.2020035459
A. N.
Skrypnik
Kazan National Research Technical University named after A.N. Tupolev (KAI), 10 K. Marx
Str., Kazan, Republic of Tatarstan, 420000, Russia; Technical University of Dresden, Dresden, 01069, Germany
A. M.
Ermakov
Kazan National Research Technical University named after A.N. Tupolev, 15 K. Marx Str., Kazan,
Republic of Tatarstan, 420111, Russia
R. T.
Kalimullin
Kazan National Research Technical University named after A.N. Tupolev, 15 K. Marx Str., Kazan,
Republic of Tatarstan, 420111, Russia
A. A.
Mironov
Kazan National Research Technical University named after A.N. Tupolev (KAI), 10 K. Marx
Str., Kazan, Republic of Tatarstan, 420000, Russia
Igor A.
Popov
Department of Theoretical Heat Engineering Foundations, Kazan State Technical Tupolev's University, Russia, 420111 Kazan, K.Marx Str. 10.
A. D.
Chorny
A.V. Luikov Heat and Mass Transfer Institute, National Academy of Sciences of Belarus,
15 P. Brovka Str., Minsk, 220072, Belarus; National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow,
Russia
Yu. V.
Zhukova
Turbulence Laboratory, A. V. Luikov Heat and Mass Transfer Institute, National Academy of Sciences of Belarus, P. Brovka Str. 15, 220072 Minsk, Belarus
G. S.
Marshalova
A.V. Luikov Heat and Mass Transfer Institute, National Academy of Sciences of Belarus,
15 P. Brovka Str., Minsk, 220072, Belarus
air cooling apparatus
heat carrier
convective heat transfer
hydraulic losses
heat transfer enhancement
experiment
numerical simulation
The objective of the present study was to check the approaches of numerical simulation of a finned-tube oil radiator of power engineering devices, cooling systems of compressor stations, etc. The additional tasks were to define thermal and hydraulic characteristics of an oil radiator without field tests and to reveal possible design defects. In the course of the study, the obtained experimental data, the engineering calculations, and the numerical simulation results of finned-tube oil radiator characteristics are compared.
ULTRASOUND-ASSISTED ENHANCEMENT OF HEAT TRANSFER IN STAGGERED PIPES
1273-1288
10.1615/HeatTransRes.2020034607
Dongwei
Zhang
Center on the Technology and Equipments for Energy Saving in Thermal Energy System of MOE,
School of Mechanical and Power Engineering, Zhengzhou University, Zhengzhou, Henan, 450001,
China
Zhuantao
He
Center on the Technology and Equipments for Energy Saving in Thermal Energy System of MOE,
School of Mechanical and Power Engineering, Zhengzhou University, Zhengzhou, Henan, 450001,
China
Erhui
Jiang
Center on the Technology and Equipments for Energy Saving in Thermal Energy System of MOE, School of Mechanical and Power Engineering,
Zhengzhou University, Zhengzhou, Henan 450001, China; Institute of Refrigeration and Cryogenics, School of Mechanical Engineering,
Shanghai Jiao Tong University, Shanghai 200240, China
Chao
Shen
Zhengzhou University
Junjie
Zhou
Center on the Technology and Equipments for Energy Saving in Thermal Energy System of MOE,
School of Mechanical and Power Engineering, Zhengzhou University, Zhengzhou, Henan, 450001,
China
Meiyu
Du
Center on the Technology and Equipments for Energy Saving in Thermal Energy System of MOE,
School of Mechanical and Power Engineering, Zhengzhou University, Zhengzhou, Henan, 450001,
China
ultrasonic
heat transfer enhancement
simulation
CFD analysis
pipes
Development of renewable energy technology and improvement of energy efficiency have currently become necessary. In particular, active ultrasonic cavitation has attracted a great deal of attention in the enhancement of heat transfer efficiency, and this has been investigated in the current work using numerical methods. A physical model and associated simulation methods are first introduced. Next, the influence of various operational parameters on heat transfer enhancement are presented and analyzed. Finally, simulations with different configurations, with the inclusion of ultrasonic vibrations, are presented. The results show that the average outlet temperature and Chilton and Colburn factor j rise with increasing ultrasonic amplitudes and Reynolds numbers, but decrease with increasing ultrasonic frequencies. The friction factor f decreases with similar changes in parameters. The optimum values obtained for Reynolds number and ultrasonic frequency are 63.5 and 20 kHz, respectively. Additionally, the ultrasonic vibrations enhanced the heat transfer performance at the front and back pipe walls. It is recommended that ultrasonic vibrations be applied at pipe locations with fully developed flow.
UPGRADING THE PERFORMANCE OF HEAT RECOVERY UNIT CONTAINING HEAT PIPES BY USING A HYBRID (CuO + ZnO)/WATER NANOFLUID
1289-1300
10.1615/HeatTransRes.2020035393
Adnan
Sözen
Department of Energy Systems Engineering, Faculty of Technology, Gazi University, Ankara,
Turkey
Kerim
Martin
Energy Systems Engineering Department, Gazi University, Ankara, Turkey; Department of Energy Systems Engineering, Elbistan Engineering Faculty, Kahramanmaraş İstiklal Üniversity, Kahramanmaraş, Turkey
İpek
Aytaç
University of Turkish Aeronautical Association
Çağdaş
Filiz
Kilis 7 Aralık University, Kilis, Turkey
heat pipe
heat recovery
hybrid nanofluid
Waste heat recovery system is a system using for preheating fresh air needed in industrial and waste heat plants. The aim of this study is to improve the performance of a heat recovery unit by using a heat exchanger consisting of a heat pipe which uses a (CuO + ZnO)/water hybrid nanofluid as a working fluid. As is known, the nanofluid in the heat pipe is able to evaporate at a temperature lower than the temperature of the base fluid, so the heat recovery unit will also be provided to benefit from the waste heat at lower temperatures. Thus, the temperature range of the heat recovery unit will be increased. The optimum conditions for the evaporation of hybrid nanofluid in the evaporator region of the heat pipe were investigated by performing experiments at different temperatures and flow rates of the waste heat. Similar conditions were made in a cold fluid, and the optimum conditions for condensing the nanofluid in the condenser region were investigated. Experiments were performed at 2 different cold air flows (30 g/s and 60 g/s), 3 different hot air flows (50 g/s, 70 g/s, and 90 g/s) and 2 different heating powers (1000 W and 2000 W). Thus, optimum values of temperature and flow were found at all Re numbers on the hot- and cold-fluid sides, and it was helped to determine the operating temperature ranges of the heat recovery unit. The efficiency improvement rates in the heat pipe were between 14% and 73%. The best result was achieved when the cold-air duct Reynolds number was 6700 and the hot-air duct Reynolds number was 11,250. The use of the hybrid nanofluid at all Re numbers reduced thermal resistance in the heat pipe. The maximum reduction rate in thermal resistance was achieved to be 40.4% compared to pure water when the cold-air duct Reynolds number was 12,400. As a result, the efficiency of the heat tension recovery unit increased.
TEMPERATURE OSCILLATION MECHANISM OF A FLAT-TYPE LOOP HEAT PIPE
1301-1315
10.1615/HeatTransRes.2020034240
Dongxing
Gai
School of Energy and Power Engineering, Wuhan Institute of Technology, 430205, China
loop heat pipe (LHP)
temperature oscillation
two-phase flow instability
criterial formula
Unstable operations like temperature oscillation often occur in loop heat pipes (LHPs) and therefore restrict their applications. Such instability issues are strongly related to the LHP structure, heat load, working fluid, filling ratio, gravity acceleration, and other factors. The mechanism of temperature oscillation of LHP is studied both experimentally and theoretically by investigating the vapor-liquid two-phase flow and its instability, which is directly related to temperature oscillation. A unique criterion formula was found to predict the occurrence of flow-related temperature oscillation. The results were validated by experiment. The study provides a theoretical basis for exploring ways to suppress temperature oscillations of LHPs.
THERMODYNAMIC ASSESSMENT OF ULTRA-LOW-GLOBAL WARMING POTENTIAL REFRIGERANTS FOR SPACE AND WATER HEATERS
1317-1335
10.1615/HeatTransRes.2020035317
Luis
Sánchez-Moreno-Giner
Institu to Universitario de Investigación en Ingeniería Energética, Universitat Politècnica de València, 46022, Valencia, Spain
Emilio
López-Juárez
Institu to Universitario de Investigación en Ingeniería Energética, Universitat Politècnica de València, 46022, Valencia, Spain
José
Gonzálvez-Maciá
Institu to Universitario de Investigación en Ingeniería Energética, Universitat Politècnica de València, 46022, Valencia, Spain
Abdelrahman H.
Hassan
Institu to Universitario de Investigación en Ingeniería Energética, Universitat Politècnica de València, 46022, Valencia, Spain; Mechanical Power Engineering Department, Faculty of Engineering, Zagazig University, Zagazig
44519, Egypt
heat pump
water heaters
ultra-low-GWP refrigerants
pinch point
thermal match
The current paper studies the most suitable ultra-low-global warming potential (GWP) (GWP < 30) candidates in the market, considering also its grade of flammability and toxicity, for heat pumps employed for different space heating and domestic hot water (DHW) applications. A pre-design thermodynamic model has been developed to evaluate the performance and size limits for any subcritical or transcritical heat pump under certain working conditions. This generic model is based on the pinch point approach, so it does not depend on a certain type of heat exchangers, it only depends on the external working conditions. The results showed that all subcritical ultra-low-GWP, nonflammable, and nontoxic refrigerants considered have either lower coefficient of performance (COP) or volumetric heating capacity (VHC) compared with the reference high-GWP refrigerants R-410A and R-134a. Additionally, the only refrigerants with higher COP, such as R-717 (ammonia) or R-290 (propane), are either extremely flammable or toxic. For the applications need of high water-side temperature lift, the transcritical refrigerants R-744 (CO2) and R-170 (ethane) showed the best performance, regarding both COP and VHC values, of all the refrigerants studied. The refrigerants R-161, R-1270 (propylene), and R-1234yf presented a balanced performance in both space heating and DHW applications. This makes them potential candidates to be employed in subcritical multi-temperature levels heat pumps.
A CONJUGATE MODEL FOR BUBBLE GROWTH IN LOW-VELOCITY SUBCOOLED FLOWS
1337-1350
10.1615/HeatTransRes.2020034568
Maryam
Medghalchi
Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Canada,
M5S3G8
Nasser
Ashgriz
Department of Mechanical and Industrial Engineering, University of Toronto,
Toronto, Ontario M5S 3G8, Canada
heat exchanger
single bubble growth
flow boiling
multiphase flows
A model for the growth of a bubble on a horizontal heated surface with a constant temperature and in a subcooled condition is presented. The model considers microlayer evaporation, transient thermal boundary layer conduction, and surface condensation or evaporation. The bubble growth time is divided into several stages, and the equation describing the bubble growth is simplified for different stages using a new characteristic time, and a new characteristic size. Several analytical solutions for the bubble growth are obtained at the early stages of the bubble growth and before the bubble lifts off. It is shown that before a critical time, the bubble growth is mainly governed by microlayer evaporation, however after the critical time the bubble growth is controlled by surface evaporation.