Characteristics of Air Flow and Heat Transfer in Serpentine Condenser Pipes with Attached Convection Plates in Open Channel
Corresponding email: edymesin80@unsam.ac.id
Published at : 21 Jul 2020
Volume : IJtech
Vol 11, No 3 (2020)
DOI : https://doi.org/10.14716/ijtech.v11i3.2583
Susanto, E., Alhamid, M.I., Nasruddin, Budihardjo, Prabowo, Novianto, S., 2020. Characteristics of Air Flow and Heat Transfer in Serpentine Condenser Pipes with Attached Convection Plates in Open Channel. International Journal of Technology. Volume 11(3), pp. 564-573
| Edy Susanto | Department of Mechanical Engineering, Faculty of Engineering, Universitas Medan Area, Medan 20112, Indonesia |
| M. Idrus Alhamid | Department of Mechanical Engineering, Faculty of Engineering, Universitas Indonesia, Kampus UI Depok, Depok 16424, Indonesia |
| Nasruddin | Department of Mechanical Engineering, Faculty of Engineering, Universitas Indonesia, Kampus UI Depok, Depok 16424, Indonesia |
| Budihardjo | Department of Mechanical Engineering, Faculty of Engineering, Universitas Indonesia, Kampus UI Depok, Depok 16424, Indonesia |
| Prabowo | Department of Mechanical Engineering, Sepuluh Nopember Institute of Technology, Surabaya 60117, Indonesia |
| Sentot Novianto | Department of Mechanical Engineering, Faculty of Engineering, Universitas Trisakti, Jakarta 11440, Indonesia |
Many efforts have been made to reduce
the energy consumption of household refrigerators. One method is to place the
pipe condenser to increase the rate of heat release. This numerical study
examines the effect of changing the gap ratio on the flow characteristics and
natural convection heat transfer of 20 pipes attached vertically to the
convection plate with aluminum foil coating. The gap ratio was varied between
1.05 and 4.20 using ANSYS-FLUENT software to obtain velocity vector,
temperature contour, tangential velocity, and local Nusselt number, both inside
and outside the channel. With the change in gap ratios from 1.05 to 2.10, the
rate of heat transfer increased significantly, reaching 2.2% while tangential
velocity also increased considerably. At gap ratios of 3.15 and 4.20, the rate
of heat transfer increased more gradually, local Nusselt number increased
slightly where the influence of convection walls was smaller, and tangential
velocity showed a very small increase. Flow characteristics were similar, with
air flowing upward across the inner and outer channels.
Gap ratio; Household refrigerator; Natural Convection; Nusselt Number; Vertical Channel
Household refrigerators are an important part of daily life, and researchers have made many attempts to make them more energy-efficient. Several factors contribute to the energy-efficiency of household refrigerators, including consumer behavior and heat dissipation. One factor in consumer behavior that affects refrigerator energy consumption has been demonstrated by Susanto et al. (2018), who tested the relationship between thermostat regulation and increased energy consumption of household refrigerators. The relationship between refrigerator energy consumption and heat transfer factors was investigated by Sefcik et al. (1991) conducted experiments on natural convection behavior in enclosures that were ventilated at the lower and upper ends to provide air flow to improve heat transfer. In his experiment, the average Nusselt number changed according to the size of the two ventilation holes.
Research conducted by Davies
et al. (2000) found that changes in free air temperature affect the
Nusselt number: the higher the free
air temperature the lower the Nusselt number. Chouikh
et al. (1998) conducted a numerical study for natural convection flow along a range of two
isothermal horizontal pipes by varying the Rayleigh number (Ra) and pipe
spacing (Ra was used to determine the laminar to turbulent transition from the
flow of natural convection boundary layers). The results showed that Ra
increased and the air temperature gradient in the pipes was steeper so that the
rate of heat transfer increased, and vice versa. Manca
et al. (2002) studied natural convection heat-transfer characteristics using of discrete heated plates parallel slope
variations; they tested the hypothesis that at an angle smaller than 85o
air flow would move outside
thereby increasing the temperature inside the channel. Manca
et al. (2002) studied the characteristics of natural convection heat
transfer using; it is stated that at a slope angle <85o it causes an inflow
of air from the upper side which prevents the outflow of air thereby increasing
the temperature in the channel. Buonomo et al.
(2017) studied two horizontal parallel walls by filling the stem with
porous media, finding that the use of
porous media resulted in an increase in heat transfer. Dehghandokht
et al. (2011) performed numerical analysis on a multiport serpentine
meso-channel heat exchanger. Their simulation showed that the effect of
serpentine bends on heat exchangers will increase average heat transfer by
almost 20% compared with those using
straight plates.
Lewandowski et al.
(2018a) observed natural convection by varying channel width and wall temperature, the
results finding that wider air ducts caused significantly heat transfer. Ospir et al. (2012) investigated dynamic flow in
vertical plate channels with Rayleigh numbers and gap ratio modification; they
used laser tomography to visualize flow, finding that a larger gap ratio causes
the length of the upper cell to decrease. Alzwayi et
al. (2014) performed numerical simulations to investigate the effect of
channel width on transition flow under various plate temperatures, using the k-tur turbulence model to simulate flow and
thermal fields in the channel; their
results showed that the transition flow in isothermal cases is slower than
adiabatic cases.
Lewandowski et al. (2018b) investigated the distribution and loss
of heat from building walls using a Thermal Imaging Camera (TIC). they found
that the use of infrared cameras made it possible to determine local heat loss. Lewandowski et al.
(2017) also analyzed convection heat transfer to two
parallel and vertical plates where the slit plate-width varies; infrared observation showed there was a relationship
between the width of the gap and the rate of heat transfer.
The above studies generally conclude that the heat transfer observed occurs through natural convection.
In natural convection, fluid flows due to differences in density caused by
differences in temperature (buoyancy) and the absence of external influences
such as fans. Serpentine pipe bends cause an increase in heat transfer. The
novelty of this research is the combination of serpentine pipe bends that are
attached to vertical plates, providing space for air flow. This is of interest
because it causes a greater increase in heat transfer. The purpose of this
research is to study the numerical effect of changing the gap ratio on the flow
characteristics and natural convection heat transfer from 20 pipes that are
mounted vertically to the convection plate with a layer of aluminum foil.
The numerical results obtained by varying the gap ratio from 1.05 to
4.20 led to the following conclusions: (1) The increase in the gap
ratio from 1.05 to 2.10 caused a significant increase in the total
condenser heat transfer (an increase of 2.2% or 6.33 Watt); (2) Because
the pipe was attached to the convection plate, the air velocity, tangential
velocity, and Nusselt number are increased. This causes
the upstream and downstream areas to be vortex-dominated, which has a positive
impact on heat transfer characteristics; (3) The air flow characteristics
inside the canal tend to be the same, where free air moves from the bottom
upward in the canal and convection wall due to buoyancy; (4) On the side of the
pipe that adheres to the convection plate,
tangential velocity and Nusselt number are zero because
there is no air flowing on the side of the pipe.
The
author would like to thank the Doctor Dissertation Research Grant (PDD) from
the Indonesia Ministry of Research and Higher Education for funding this
research (contract no. 088/SP2H/LT/DRPM/2018).
Alzwayi, A.S., Paul, M.C., 2014. Transition of
Free Convection Flow between Two Isothermal Vertical Plates. International Journal of Heat and Mass
Transfer, Volume 76, pp. 307–316
Buonomo, B.,
Diana, A., Manca, O., Nardini, S., 2017. Local Thermal Non-equilibrium
Investigation on Natural Convection in Horizontal Channel Heated from Above and
Partially Filled with Aluminum Foam. Journal
Energy Procedia, Volume 126, pp. 42–49
Chouikh, R.,
Guizani, A., Maalej, M., Belghith, A., 1998. Numerical Study of the Laminar
Natural Convection Flow around Horizontal Isothermal Cylinder. Renewable Energy, Volume 13(1), pp. 77–88
Davies, M.R.D.,
Newport, D.T., Dalton, T.M., 2000. On Gaseous Free-convection Heat Transfer with
Well-defined Boundary Conditions. Journal
of Heat Transfer, Volume 122(4), pp. 661–668
Dehghandokht, M.,
Khan, M.G., Fartaj, A., Sanaye, S., 2011. Flow and Heat Transfer
Characteristics of Water and Ethylene Glycol-water in a Multi-port Serpentine
Meso-channel Heat Exchanger. International
Journal of Thermal Sciences, Volume 50(8), pp. 1615–1627
Manca, O.,
Nardini, S., Naso. V., 2002. Effect on Natural Convection of the Distance between
an Inclined Discretely Heated Plate and A Parallel Shroud Below. Journal of Heat Transfer, Volume 124(3),
pp. 441–451
Ospir, D., Popa,
C., Chereches, C., Polidoro, G., Fohanno, S., 2012. Flow Visualization of
Natural Convection in a Vertical Channel with Asymmetric Heating, International Communications in Heat and
Mass Transfer, Volume 39(4), pp. 486–493
Pujowidodo, H., Siswantara,
A.I., Budiarso, Gunadi, G.G.R., Daryus, A., 2018. Turbulence Model and
Validation of Air Flow in Crossflow Turbine Nozzle. In: AIP Conference Proceedings, 2018, AIP Publishing, Volume
2001(1)
Ramdlan, G.G.G.,
Siswantara, A.I., Budiarso, B., Daryus, A., Pujowidodo, H., 2016. Turbulence Model
and Validation of Air Flow in Wind Tunnel. International
Journal of Technology, Volume 7(8), pp. 1362–1372
Sefcik, D., Webb,
B., Heaton, H.S., 1991. Natural Convection in Vertically Vented Enclosures. Journal of Heat Transfer, Volume 113(4),
pp. 912–918
Susanto, E.,
Alhamid, M.I., Nasruddin, N., Budihardjo, B., 2018. An Experimental
Investigation Into the Effect of Thermostat Settings on the Energy Consumption
of Household Refrigerators. International
Journal of Technology, Volume 9(2), pp. 364–371
Lewandowski, W.
M., Ryms, M., Denda, H., 2018a. Natural Convection in Symmetrically Heated
Vertical Channels. International Journal
of Thermal Sciences, Volume 134, pp. 530–540
Lewandowski, W.
M., Ryms, M., Denda, H., 2018b. Quantitative Study of Free Convective Heat
Losses from Thermodynamic Partitions using Thermal Imaging. Energy & Buildings, Volume 167, pp.
370–383
Lewandowski, W.
M., Ryms, M., Denda, H., 2017. Infrared Techniques for Natural Convection Investigation
in Channels between Two Vertical, Parallel, Isothermal and Symmetrically Heated
Plates. International Journal of Heat and
Mass Transfer, Volume 114, pp. 958–969