scholarly journals EXPERIMENTAL STUDY OF HEAT TRANFER AUGMENTATION USING AIR BUBBLE INJECTION AND (Al2O3 /WATER) NANOFLUID FLOW IN DOUBLE PIPE HEAT EXCHANGERS

2021 ◽  
Vol 21 (2) ◽  
pp. 96-117
Author(s):  
Dhirgham A. Alkhafaji ◽  
Hameed K. Hamzah ◽  
Haider S. Hadi
Keyword(s):  
Heat Transfer ◽  
Cold Water ◽  
Volume Flow ◽  
Hot Water ◽  
Air Bubbles ◽  
Heat Transfer Characteristics ◽  
Flow Rates ◽  
Air Bubble ◽  
Double Pipe ◽  
Pipe Heat

In the present work, an experimental study on how to increase the heat transfer coefficient (HTC) in double pipe heat exchanger (DPHE) use of a variety of Al2O3 Nano-dispersion concentrations mixed in water as base fluid with air bubble injection for counter flow arrangement under turbulent flow conditions with (Re) Reynold number range from (6000 t0 45000) . The thermal performance of (DPHE) has been enhanced with the use of two techniques. The first, is represented by adding nanoparticles to hot water (inner pipe) raising the (HTC) inside the inner tube. Increase the volume concentration cause increase in the viscosity of the nanofluid leading to increase in friction factor .Secondly is represented by Air bubble injection in outer pipe with cold water to enhance the (HTC). The mobility of air bubbles inside the water from down to up by the force of the buoyancy, and the movement of these air bubbles results in significant mixture and turbulence within the water. The variations of number of thermal units (NTU), exergy loss, dimensionless exergy and (Nu) are evaluated. The investigated parameters were cold water volume flow rates (8, 10, 12 and14) l/min, flow in outer tube. Also, three different volume flow rates of air (12, 16 and 20) l/min mixed with water in outer tube. The volume flow rates of hot water remains constant at (8 l/min) flow in inner pipe with three volumetric concentrations of given nanofluid. The results showed that the air bubble injection throughout the tube gave maximum enhancement in heat transfer characteristics followed by the no air bubble injection. Since the enhancement in heat transfer characteristics varies linearly with the volumetric concentration of Nanofluids, Nanofluids with 0.3% of Al2O3 nanoparticles gave more enhancements in (HTC) than the case without nanofluid. The Nusselt number increased about (8% - 45%).  

scholarly journals Pengaruh Pitch Turbulator Terhadap Ntu Pada Double Pipe Heat Exchanger

2019 ◽  
Vol 3 (1) ◽  
pp. 27
Author(s):  
Mufid Mufid ◽  
Arif Rahman Hakim ◽  
Bambang Widiono
Keyword(s):  
Heat Transfer ◽  
Stainless Steel ◽  
Heat Exchanger ◽  
Transfer Rate ◽  
Cold Water ◽  
Hot Water ◽  
Energy Sources ◽  
Energy Needs ◽  
Double Pipe ◽  
Pipe Heat

Saat ini kebutuhan akan energi di dunia terus meningkat, sejalan dengan semakin tumbuhnya industri untuk menopang kehidupan manusia. Namun kenaikan kebutuhan energi tersebut tidak diimbangi dengan bertambahnya sumber energi, sehingga harga energi semakin mahal. Untuk meminimalisir kebutuhan energi, maka perlu dicari sumber-sumber energi alternatif baru, terutama sumber energi baru dan terbarukan. Disamping itu perlu dilakukan pengelolaan energi yang lebih baik, sehingga kebutuhan energi dunia bisa dikurangi. Double Pipe Heat exchanger memiliki pipa luar stainless steel dengan diameter dalam (Do) 3,5 inchi, ketebalan pipa (To) 1,5 mm, dan panjang pipa (Lo)  790mm dan pipa dalam (Di) 1 3/8 inchi,   ketebalan(Ti) 0,6 mm, dan panjang pipa (Li) 920mm, dengan air dingin dan air panas yang digunakan sebagai fluida uji di annulus dan pipa dalam. Helical turbulator dari besi (mild steel) dengan dimensi geometris jarak antar elemen (pitch) sebesar 25mm, 50 mm dan 75 mm berdiameter dalam (Di) 5/16 inchi dan diameter luar(Do) 1 5/16 inchi dengan panjang 750mm dimasukkan dalam inner tube dari heat exchanger. Air panas memasuki tabung dengan variasi flowate mulai  400 l/jam sampai 900 l/jam, sedangkan flowrate air dingin konstan 900 l/jam. Hasil penelitian dengan  disisipkannya helical turbulator   sebagai turbulator pada heat exchanger mengakibatkan peningkatan laju perpindahan kalor. Helical turbulator dengan pitch 25mm menimbulkan peningkatan laju perpindahan kalor  paling besar sebesar ±62% dibandingkan plain tube. Helical turbulator mengakibatkan peningkatan NTU heat exchanger terbesar sebesar ±63% dihasilkan oleh helical turbulator dengan pitch 25mm.At present the need for energy in the world continues to increase, in line with the growing industry to sustain human life. However, the increase in energy needs is not offset by the increase in energy sources, so energy prices are increasingly expensive. To minimize energy needs, it is necessary to look for new alternative energy sources, especially new and renewable energy sources. Besides that, better energy management is needed, so that the world's energy needs can be reduced. Double Pipe Heat Exchanger has stainless steel outer pipe with inner diameter (Do) 3.5 inch, pipe thickness (To) 1.5 mm, and pipe length (Lo) 790 mm and pipe inside (Di) 1 3/8 inch, thickness (Ti) 0.6 mm, and the length of pipe (Li) 920 mm, with cold water and hot water used as test fluid in the annulus and inner pipe. Mild steel helical turbulators with geometric dimensions of 25mm, 50mm and 75mm intervals between 5/16 inch in diameter and a 750mm length 5/16 inch outer diameter (Do) are included in the inner tube of heat exchanger. Hot water enters the tube with variations in flowate from 400 l / hour to 900 l / hour, while the cold water flowrate is constant 900 l / hour. The results of the study by inserting a helical turbulator as a turbulator in a heat exchanger resulted in an increase in the heat transfer rate. Helical turbulators with a pitch of 25mm give rise to the highest heat transfer rate of ±62% compared to plain tubes. Helical turbulators cause the largest increase in NTU heat exchanger of ±63% produced by a helical turbulator with a 25mm pitch.

Design and Experimental Research of Gas Cooler for CO2 Heat Pump Water Heater

2010 ◽  
Vol 156-157 ◽  
pp. 1161-1164
Author(s):  
Ye Feng Liu ◽  
Guo Dong Gong ◽  
Xi Chen
Keyword(s):  
Heat Transfer ◽  
Heat Pump ◽  
Hot Water ◽  
Global Environment ◽  
Heat Transfer Characteristics ◽  
Water Heater ◽  
Working Pressure ◽  
Heat Pump Water Heater ◽  
Double Pipe ◽  
Pipe Heat

The advantages of CO2 Heat Pump water heater include: CO2 is one of natural refrigerants and does not affect the global environment as many other HFCs refrigerants; CO2 heat pump water heater can produce hot water up to 90 ,which is higher than HFCs heat pump water heater(about 55 ).So the application of CO2 Heat Pump water heater is potential. But the Working pressure of CO2 Heat Pump Water Heater is about 9~12Mpa and is 3-5times of HFCs heat pump water heater’. Gas cooler is one of important part for CO2 heat pump water heater, and it must meet the needs of not only pressurization but also heat transfer. So it is important to design gas cooler correctly. In the paper, one system of CO2 Trans-critical Cycle Heat Pump Water Heater is designed, and double-pipe gas cooler is designed The heat transfer characteristics of CO2 in gas cooler with water in double-pipe heat exchanger was experimentally investigated. Experimental results showed that the gas cooler can meet the need of trans-critical CO2 cycle heat pump water heater. All the work is valuable for the application of CO2 heat pump water heater.

scholarly journals Improving thermal performance using Al2O3-water nanofluid in a double pipe heat exchanger filling with porous medium

2020 ◽  
Vol 24 (6 Part B) ◽  
pp. 4267-4275
Author(s):  
Qusay Jasim ◽  
Noah Saleh ◽  
Adnan Hussein
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Fluid Flow ◽  
Heat Exchanger ◽  
Volume Flow ◽  
Inlet Temperature ◽  
Flow Rates ◽  
Inside Diameter ◽  
Double Pipe ◽  
Pipe Heat

A double pipe heat exchanger is significant device for many industrial applications. In this paper, an experimental study using both porous media and nanofluid to enhance heat transfer in a double pipe heat exchanger is performed. The test rig has been fabricated with inner copper pipe of 1.10 m length, 16 mm, and 14 mm outside and inside diameter, respectively. While, the outer PVC pipe is 1 m length, 31 mm, and 27 mm outside and inside diameter, respectively. The inner pipe has been filling with 3 mm diameters of steel balls porous media. The experimental tests were performed utilizing alumina nanofluid (Al2O3-water) with two volume concentrations 0.5% and 1%. The volume flow-rates are in the range of (2-5) Lpm and 10 Lpm through inner and outer pipe, respectively. It was conducted with a constant 28?C inlet temperature of cold fluid-flow inside the inner pipe and 50?C inlet temperature of hot fluid-flow inside the outer pipe. Results indicated that the heat transfer enhanced as nanofluid volume concentrations and volume flow-rates increase. It was observed that effectiveness increases as increase of flow-rate and nanofluid concentrations.

scholarly journals Experimental and CFD Analysis of GW70 based Cu Nanofluids in a Parallel Flow Heat Exchanger

2021 ◽  
Vol 10 (4) ◽  
pp. 106-110
Author(s):  
M.L.R. Chaitanya Lahari ◽  
◽  
P.H.V. Sesha Talpa Sai ◽  
K.V. Sharma ◽  
K.S. Narayanaswamy ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Mass Flow ◽  
Parallel Flow ◽  
Hot Water ◽  
Cfd Analysis ◽  
Flow Rates ◽  
Mass Flow Rates ◽  
Double Pipe ◽  
Pipe Heat

The Nusselt number, overall heat transfer, and convective heat transfer coefficients of glycerol-water-based Cu nanofluids flowing in a parallel flow double pipe heat exchanger are estimated using CFD analysis. Single-phase fluid approach technique is used in the analysis. Ansys 19.0 workbench was used to create the heat exchanger model. Heat transfer tests with nanofluids at three flow rates (680<Re<1900) are carried out in a laminar developing flow zone. For testing, a 500 mm long concentric double pipe heat exchanger with tube dimensions of ID=10.2 mm, OD= 12.7 mm, and annulus dimensions of ID=17.0 mm, OD= 19.5 mm is employed. Copper is utilized for the tube and annulus material. This study employed three-particle volume concentrations of 0.2 percent, 0.6 percent, and 1.0 percent. The mass flow rates of hot water in the tube are 0.2, 0.017, and 0.0085 kg/s, while the mass flow rates of nanofluids in the annulus are 0.03, 0.0255, and 0.017 kg/s. The average temperature of nanofluids is 36°C, whereas hot water is 58°C. In comparison to base liquid, the overall heat transfer coefficient and convective HTC of 1.0 percent copper nanofluids at 0.03 kg/s are raised by 26.2 and 46.2 percent, respectively. The experimental findings are compared to CFD values, and they are in close agreement.

scholarly journals Study the Effect of Granules Type of The Porous Medium on The Heat Transfer Enhancement for Double Pipe Heat Exchanger

2019 ◽  
Vol 26 (4) ◽  
pp. 43-49
Author(s):  
Ehsan Abbas ◽  
Shagul Mohammed
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Heat Exchanger ◽  
Cold Water ◽  
Hot Water ◽  
Transfer Enhancement ◽  
Copper Pipe ◽  
Inner Diameter ◽  
Double Pipe ◽  
Pipe Heat

The current study includes the effect of the type of porous medium on the heat transfer enhancement for double-pipe heat exchanger. Using the three types of the porous medium of balls (steel, ceramic and glass) with diameters (6.35, 6 and 7) mm respectively. The tests were carried out on a locally manufactured heat exchanger, consisting of a copper pipe with an inner diameter (20mm), an outer diameter (22mm) and a length of (1800mm), fixed inside a pipe made of galvanized iron with the same length of copper pipe with inner diameter (50mm) and thickness (5mm). The heat exchanger is insulated with a layer of glass wool to prevent leakage of heat to the area surrounding the exchanger. The tests carried out on the heat exchanger in four cases, the three cases for porous medium, also the case of exchanger without porous medium, and for all cases identical operating conditions, which is inlet temperature of hot, and cold water determined at (63 and 32)˚C and the number of Reynolds from (1100 to 9750) for cold water and (415 to 7500) for hot water. The experimental results showed that the highest thermal conductivity was obtained when the ceramic balls were used, which was estimated to be approximately (219.302) W/˚C and increased by (105.3%, 10.8%, 4.3%) for cases: without porous medium, glass balls and steel balls respectively. The effect of the pressure drop in the hot water side, was recorded the highest value for pressure drop when the ceramic balls were used and ranged from (0.5 to 19.5) mmHg and increased by (0.95%, 2.25%) when compared with the results of two cases for balls (steel and glass) respectively.

An experimental investigation of heat transfer characteristics of water based Al2O3 nanofluid operated shell and tube heat exchanger with air bubble injection technique

2017 ◽  
Vol 6 (4) ◽  
pp. 83 ◽  
Author(s):  
Gaurav Thakur ◽  
Gurpreet Singh
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Al2o3 Nanoparticles ◽  
Air Bubbles ◽  
Heat Transfer Characteristics ◽  
Tube Heat Exchanger ◽  
Air Bubble ◽  
Transfer Characteristics ◽  
Water Based ◽  
Shell And Tube

The thermal performance of shell and tube heat exchangers has been enhanced with the use of different techniques. Air bubble injection is one such promising and inexpensive technique that enhances the heat transfer characteristics inside shell and tube heat exchanger by creating turbulence in the flowing fluid. In this paper, experimental study on heat transfer characteristics of shell and tube heat exchanger was done with the injection of air bubbles at the tube inlet and throughout the tube with water based Al2O3 nanofluids i.e. (0.1%v/v and 0.2%v/v). The outcomes obtained for both the concentrations at two distinct injection points were compared with the case when air bubbles were not injected. The outcomes revealed that the heat transfer characteristics enhanced with nanoparticles volumetric concentration and the air bubble injection. The case where air bubbles were injected throughout the tube gave maximum enhancement followed by the cases of injection of air bubbles at the tube inlet and no air bubble injection. Besides this, water based Al2O3 nanofluid with 0.2%v/v of Al2O3 nanoparticles gave more enhancement than Al2O3nanofluid with 0.1%v/v of Al2O3 nanoparticles as the enhancement in the heat transfer characteristics is directly proportional to the volumetric concentration of nanoparticles in the base fluid. The heat transfer rate showed an enhancement of about 25-40% and dimensionless exergy loss showed an enhancement of about 33-43% when air bubbles were injected throughout the tube. Moreover, increment in the heat transfer characteristics was also found due to increase in the temperature of the hot fluid keeping the flow rate of both the heat transfer fluids constant.

scholarly journals Simulation of the effectiveness of longitudinal rectangular fins on the efficiency of the double pipe heat exchanger

2019 ◽  
Vol 21 (4) ◽  
pp. 48-57
Author(s):  
N. F. Timerbaev ◽  
A. K. Ali ◽  
Omar Abdulhadi Mustafa Almohamed ◽  
A. R. Koryakin
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Cold Water ◽  
Tube Diameter ◽  
Hot Water ◽  
Outer Tube ◽  
Design Parameters ◽  
Double Pipe ◽  
Central Pipe ◽  
Pipe Heat

In this article, a mathematical simulation of a double pipe heat exchanger is carried out, having the longitudinal rectangular fins with the dimension of (2*3*1000) mm, mounted on the outer surface of the inner tube of the heat exchanger. In this paper, the advantage of using of that type of fins and its effect on the effectiveness of the heat exchanger are studied with the help of the computer program. The carried out research allowsmaking the calculation to find the optimum design parameters of heat exchangers. The outer tube diameter is (34.1mm) while the inner tube diameter is (16.05mm). The tubes wall thickness is (1.5mm) and the model length was (1 m). The hot water is flowing through the inner tube in parallel with the cold water that passing the outer tube. The hot and cold water temperature at the inlet is (75°C & 30°C) respectively. The mass flow rate inside the central pipe is (0.1 kg/s) while the annular pipe carrying (0.3 kg/s). In the present work, the program ANSYS Workbench 15.0 was used to find out the results of heat transfer as well as the behavior of liquids inside the heat exchangers.

Optimizing Effectiveness of Double Pipe Heat Exchanger Using Nanofluid and Different Porous Fins Arrangement

2021 ◽  
Author(s):  
Avinash Kumar ◽  
Vinay Arya ◽  
Chirodeep Bakli
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Design Parameters ◽  
Heat Transfer Characteristics ◽  
Pressure Losses ◽  
Porous Fin ◽  
Transfer Characteristics ◽  
Porous Fins ◽  
Double Pipe ◽  
Pipe Heat

Abstract A numerical study is carried out to investigate the effect of porous fins in counter-flow Double Pipe Heat Exchanger (DPHE). Four DPHE with different porous fin arrangements is simulated for varying Darcy number, fin height, and the number of fins and compared with the conventional DPHE with no porous fins. The Darcy-Brinkman-Forchheimer equation is employed to model the flow in the porous fins considering fixed Re = 100. Al2O3-H2O nanofluid and water are used as hot and cold fluids respectively. Stainless steel is used as porous material with a porosity of 0.65. Results are evaluated in terms of effectiveness and Performance Evaluation Criterion (PEC). The effectiveness of the heat exchanger is used to analyze the heat transfer characteristics whereas the PEC is used to analyze the heat transfer characteristics considering pressure losses also. We evaluated maximum enhancement in thermal performance using effectiveness analysis and through PEC study we evaluated optimal effectiveness and corresponding design parameters. It is shown that utilizing porous fins in DPHE enhances the heat transfer by 134.3%. However, along with enhancement in heat transfer, the pressure losses also enhance which makes the application of porous fin non-viable. Therefore, using the PEC study we obtained optimal design parameters (Da = 10−3, hf = 4 cm, and n = 30) which adapts porous fin viable with enhancement in heat transfer by 66.38%.

Sign in / Sign up

Export Citation Format

Share Document