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i n t e r n at a t i o n a l j o u r n a l o f r e f r i ge g e r a t io i o n 7 8 ( 2 0 1 7) 7) 1 – 1 7
Available online at www.sciencedirect.com
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j o u r n a l h o m e p a g e : w w w . e l s e v i e r. r. c o m / l o c a t e / i j r e f r i g
Review
Review of nature-inspired heat exchanger technology Zhiwei Huang, Yunho Hwang * Hwang *,, Reinhard Radermacher Center for Environmenta Environmentall Energy Engineering, Department of Mechanical Engineering, University of Maryland, 4164 Glenn L. Martin Hall Bldg., College Park, MD 20742, USA
A R T I C L E
I N F O
Article history:
Received 5 October 2016 Received in revised form 15 February 2017 Accepted 6 March 2017 Available Availa ble online 8 March 2017 Key words:
Nature-inspired Heat exchanger Fractal Surface wettability Evaporative condenser Biomimicry
A B S T R A C T
The enormous heat and mass transfer phenomena in nature have led engin solutions for heat transfer enhancement problems from nature. In a current s prehensive review review of nature-inspire nature-inspired d heat exchanger technology is presented, on fractal geometries, heat exchanger surface wettability control and evapora Fractal geometry, widely found in respiratory systems and vascular systems o animals, has been introduced into heat transfer area because of its intrinsic minimized flow resistance and strong heat transfer capability. Plant leaves w surface wettability inspire heat exchanger surface treatment for condensatio ing application. Evapor Evaporation ation of perspirat perspiration ion to regul regulate ate human temperature en application of evaporative evaporative condensers. Based on a review review,, an outline for applyin to heat exchanger design has been developed. Promising natural phenomena phenomena for are discussed. This review is expected to motivate future research on naturetransfer devices. 2017 Elsevier Ltd and IIR. All rig Read Free Foron 30this Days Sign up to©vote title
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Étude de la technologie des échangeurs de chaleur inspi
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i n t e r n at i o n a l j o u r n al o f r e f r i ge r a t io n 7 8 ( 2 0 1 7 ) 1 – 1 7
Nomenclature
Symbols AR aspect ratio C p specific heat (kJ·kg 1·K 1) D dimension f friction factor −
FC jm m
m PC Re SC wre θ c θ A θ R
−
fractal channel mass transfer Colburn factor mass (kg) total number of branching levels parallel channel Reynolds number serpentine channel retained water ratio contact angle (deg) advancing contact angle (deg) receding contact angle (deg)
Subscripts def defrosting re retained
have not been applied in current technologies but a potential are also summarized in this table. Th inspired heat exchange applications reviewed in include fractal heat exchange devices, heat exchan wettability control and evaporative cooling.They ar in details andresearchgaps are discussed.At theend how to apply natural mechanisms to heat exchang
2.
Fractal heat exchanger devices
Fractal geometries are widely found in respiratory vascular systems of plants and animals, and have ducedinto heat transferarea because oftheirintrin of minimized flow resistance and strong heat transf ity. In thissection, we firstreview thefractaltheory andthen we discuss themodel development forfra changer devices with a focus on assumptions. W main findings and mechanisms for the phenomena design parameters affecting the thermal and hydrau mance. To close we summarize the research gaps. 2.1.
Fractal theory
Much research has been done to develop the frac 1997, 2002, 2003; Bejan and Lorente, 2006, 2 is one of the main research domains of adapting the heat You're Reading(Bejan, a Preview Bejan et al., 2008; Mandelbrot, 1982; Murray, 1926; and mass transfer phenomenon in the nature. Though plenty 1981;a West, 1997; Xu and Yu, 2006 ), and the major Unlock full access with free trial. nature-inspired heat exchanger designs were proposed and summarized in Table 2. studied, they are neither recognized as products of biomimicry nor systematically reviewed and studied in the past. Current Download With Free Trial study aims to give a comprehensive review of nature-inspired 2.2. Model development heat exchangers in literature. Enormousheat exchange devices are inspired by the nature, Fractal theory has been applied in different kinds as shown in Table 1. Heat and mass transfer phenomena that change devices, but mostly in heat sinks for electron
Master your semester with Scribd Read Free Foron 30this Days Sign up to vote title Table 1 – Heat transfer in nature and corresponding heat exchange application. & TheTypeNew York Times Useful inspired Not useful Nature phenomena Heat exchange application Special offer for students: Leaf Onlyvein $4.99/month. Plant structure
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Fractal channel ( Wang et al., 2010) Micro-reactor (Chen et al., 2011)
Ben
Heat transfer enh Pressure drop red
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i n t e r n at i o n a l j o u r n a l o f r e f r i ge r a t io n 7 8 ( 2 0 1 7) 1 – 1 7
Table 2 – Fractal theory development. Researchers Murray, 1926 Sherman, 1981
Mandelbrot, 1982 West, 1997 Bejan et al., 2008; Bejan and Lorente, 2006, 2007, 2011; Bejan, 1997, 2002, 2003 Xu and Yu, 2006
Main findings
Developed Murray’s law: The cube of the radius of a parent branch equals the cubes of the radii of daughter branches. Found when Murray’s law was obeyed a functional relationship exists between diameters and various flow characteristics such as wall shear stress, velocit pressure gradient. Described fractal structure from nature: coastlines, leaves and clouds. Developed scaling laws for a bulk fluid transport problem to minimize the flow Developed Constructal Theory: For a finite-size flow system to persist in time (t its configuration must evolve in such a way that it provides an easier access to currents that flow through it. Analyzed the transport properties including electrical conductivity, heat condu convective heat transfer, laminar flow, and turbulent flow in the networks and a the scaling exponents of the transport properties in the networks.
which we reviewed in detail. Table 3 is a summary of reinvestigate the thermal and hydraulic performan search for heat sinks with single-phase fluid. No. 3 in the table heat sinks, but experimental work is insufficient. is study of fuel cells, which we included due to its role in modTable 3, only few research (numbers 6, 10, 12 and eling. Different shapes have been studied in literature. Fig. 1 experimental work. (a) and (b) shows the two main shapes used as fractal heat sink. Models in literature have been developed o Fig. 1 (a) is the disk shape with inlet in the middle and outlet, decades and summarized in Table 3. The researc which is at the end of mth level branch, on the edge of the eliminate the simplicity of assumptions to mak circle. In the literature, the disk shape fractal heat sink studied closer to the reality, but a simple model is still appl is one layer structure so that the medium flows through the certain circumstances, and have the advantage o channel radially and is collected at the circle edge using an Here are some discussions about the main assum annular plenum. Fig. 1 (b) is the rectangular shape withReading inlet are made in the model listed in Table 3. You're a Preview in the middle and outlet scattering in the rectangular space. Unlock access with free trial. 1: Almost all models assumed lami In Fig. 1, the branch angle, which is defined as the anglefull of two • aAssumption branches, is 180°; however,this angle can vary and another rectneglected the heat loss to environment. angular shape with the branch angle of 180° +180° is shown in • Assumption 2: Most models did not account f Download With Free Trial Fig. 2. For rectangular shape, some research have opted for twoof gravity but Guo et al. (2014) pointed out tha layer sandwich structure as illustrated in Figs. 3 and 4. Plenty force could result in uneven bifurcation, leading of research have been done to analytically and numerically distribution. This is especially the case when
MasterTable your semester with Scribd 3 – Summary of modeling work for fractal heat sinks. Researcher Shape & The No. New York Times Pence, 2002 Special offer 1for students: Only $4.99/month. Disk 2 3
Chen and Cheng, 2002 Senn and Poulikakos, 2004
Rectangular R ta la
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1-D 1-D 3D
1, 2, 3a +3b, 4a, 5a 1, 2, 3a, 4a, 6a 1 2 3b 4b 5a 6a
Experi
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i n t e r n at i o n a l j o u r n al o f r e f r i ge r a t io n 7 8 ( 2 0 1 7 ) 1 – 1 7
Outlet
Outlet
Inlet
Branching angle=180°
Inlet
Fig. 1 – Two main shapes of fractal heat sinks: disk shape (a) and rectangular shape (b) ( Pence, 2002
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length is not long enough for the flow to be fully developed and thermal development lengths were negligib Unlock full access withpared a freeto trial. again after the bifurcation. the channel lengths, could be true if • Assumption 3: Senn and Poulikakos (2004) pointed out that diameter ratio was very high for the flow channe Chen and Cheng’s (2002) analytical analysis, in which the Reynolds number was rather small). Otherwi Download With Free Trial assumption of both thermally and hydrodynamically desumption was not applicable and the flow veloped flows was only appropriate when the hydrodynamic assumed to be developing flow. • Assumption 4: In the early stage research perio and Chen and Cheng (2002) assumed that the ef furcation on heat transfer and pressure drop wer but Alharbi et al. (2003) observed pressure reco Read Free Foron 30this Days Sign up to vote title furcations so that the prediction of pressure dro Useful Not useful if the Cancel higher effectanytime. of bifurcation was neglected Poulikakos (2004) and Wang et al. (2007) also f Special offer for students: Only $4.99/month. sure drop from bifurcation wassubstantial and
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Fig. 4 – Image of the mid-plate for aluminum fractal heat sink. (a) Top surface and (b) bottom surface ( Chen et to a finding of hotspots at highest branches which was not observed in previous research using constant wall flux (Senn and Poulikakos, 2004).
in three-dimensional simulation and poin this was due to the tapered increase in cross which acts similarly to a “diffuser” follow furcation. And the pressure recovery is lar In summary, more complicated assumptions are more higher order daughter branches, which h accurate and closer to reality, thus is recommended by the branching angles. The magnitude of the authors. ery also depends upon the flow path take asymmetry of each bifurcation (Alharbi et al et al., 2007). Boundary layer reinitiation 2.3. Major findings and mechanism discussion You're Reading a Preview sure drop forming a non-linear relationsh The major findings from fractal heat sink studies are summamass flow rate, unlike the linear relationsh Unlock full access with a free rized in Table 4. The similarities and differences are discussed leltrial. heat sink (Hong et al., 2007). Thus, we first, followed by the discussion of design parameters’ effects to apply FC in low flow rate case in practice on the performance. Download With Freemost Trialadvantage of pressure drop. Improv ture uniformity can be achieved by the incre (1) Performance of fractal channel (FC) compared with that of parent channels and branch levels. Wan of serpentine channel (SC): It was found that FC had demonstrated that fractal channels could larger heat transfer capability and more than 50% lower reduce the potential thermal damage by redu pressure drop (Chen et al., 2010; Senn and Poulikakos, of accidental blockage of channel segment (FC) com 2004; Wang et al., 2006), and an inherent advantage of (2) Performance of fractal channels Read Free Foron 30this Days Sign up to vote title (2002 uniform temperature on the heating surface (Chen et al., those of parallel channels (PC): Pence Useful Not useful yielded lower pressure drop than P 2010; Wang et al., 2006).This was compared with SC with FC a 60% Cancel anytime. the same heat transfer area, rectangular area and inlet convective heat transfer and heat sink areas Special offer for students: Only $4.99/month. channel dimensions at the same Reynolds number. The total flow rate and a 30 °C lower wall tempe
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i n t e r n at i o n a l j o u r n al o f r e f r i ge r a t io n 7 8 ( 2 0 1 7 ) 1 – 1 7
Table 4 – Summary of major findings in research on fractal heat sinks. Ref. Major findings Pence, 2002
Compared with PC with equal surface area, FC has: 1. 60% lower pressure drop for the same total flow rate and 30 °C lower wall temperature under ident pumping power conditions. 2. 50% lower density with similar maximum wall temperatures and pressure drop.
Chen and Cheng, 2002
Compared with PC with equal surface area, FC has: 1. Higher total heat transfer rate. 2. Lower total pressure drop. 3. Larger fractal dimension or a larger total number of branching levels will result in a stronger heat t capability with a smaller pumping power.
Senn and Poulikakos, 2004
1. Compared with SC with same heat transfer area and same rectangular area, FC has larger heat tr capability and 50% lower pressure drop. 2. Pressure drop from bifurcation is substantial and not negligible. 3. Lower pressure results from the not fully developed flow in higher branching level. 4. Secondary flow motions initiate at bifurcations. 5. Transverse vortices create recirculation at bifurcations that results in hot spots at the inner corner bifurcations. 6. Longitudinal vortices result in enhanced thermal mixing and a decrease in the required flow rate fo heat transfer. 7. Laminar mixing by secondary flow motions improves local Nusselt number.
Alharbi et al., 2003
Compared with Pence’s 1-D model, the 3-D model: 1. Predicts a 20% lower total pressure drop for fractal channels but similar for straight one; this is due pressure recovery at bifurcations that results from an increase in flow area. 2. Predicts pressure drop 17% higher for SC when using temperature dependent properties, but simila 3. Has the reinitiating assumption, which seems to provide plausible trends in pressure distribution. You're Reading a Preview
Alharbi et al., 2004
1. FC has 75% lower temperature variation and a 10% pressure-drop penalty compared with the PC. Unlock full access with a free trial. 2. The assumption of constant properties is not suitable for high heat flux condition.
Enfield et al., 2004
1. Developed a 2-D model for predicting concentration profiles and degree of mixing (DoM). Download With Free Trial 2. Developed a non-dimension number and a design guideline to determine the optimal number of b levels to minimize pressure drop and maximize DoM for a fixed initial parent channel width, total length, and channel depth.
Wang et al., 2006
Compare FC with PC and SC, FC has: 1. The best temperature uniformity. 2. Lower pressure drop than SC but higher pressure drop than PC. Read Free Foron 30this Days Sign up to vote title 3. Reduced risk of accidental blockage of channel segments. 4. Reduced potential of thermal damage due to the reduced risk of blockage. Useful Not useful Cancel anytime. 5. Increased number of parent channels and branch levels resulted in increased temperature uniform
Master your semester with Scribd & The New York Times Special offer for students: Only $4.99/month. Wang et al., 2007
1. Pressure drop increases as bifurcation angle increases with a decreasing increasing rate and 30°
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i n t e r n at i o n a l j o u r n a l o f r e f r i ge r a t io n 7 8 ( 2 0 1 7) 1 – 1 7
Table 4(continued)
Ref.
Major findings
Chen et al., 2010
1. FC has considerable advantages over SC in both heat transfer and pressure drop. 2. FC has inherent advantage of uniform temperature on the heating surface than SC. 3. The local pressure loss due to confluence flow is found to be larger than that due to diffluence flo
Wang et al., 2010
1. Leaf-like flow networks have lower pressure drop and higher heat transfer coefficient than symm tree-like ones.
Yu et al., 2012
1. FC has a much higher heat transfer coefficient at the cost of a much higher pump power compar with the same heat transfer area. 2. AR (aspect ratio = height/width) of microchannels plays a very important role when considering p loss, heat transfer coefficient, and COP. 3. FC with lowest AR has the highest COP, but the one with the highest AR has the highest ratio of C COP of PC.
Zhang et al., 2013
1. Small aspect ratio is preferred for a smaller pressure drop and a larger heat transfer rate. 2. A high branching level produced a high pressure drop and a large heat transfer rate. 3. The bends with fillets for the fractal-like microchannel reduce the local minor pressure losses, co with that with the 90° bends, resulting in a lower overall pressure drop.
Zhang et al., 2015
1. Both the flow rate and the AR have large influences on the evolution of the vortices, which promo mixing and enhance the efficiency of heat transfer. 2. FC with a smaller AR of 0.333 was verified to have lower pressure drop and better heat transfer pe within all the other microchannel networks under investigation in the study. 3. Observed transverse and longitudinal vorticities, secondary flow and recirculation flow motions. 4. Confluence flow has a larger pressure drop than diffluent flow, but not much difference.
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access with a free trial.to investigate the heat transfer perf (3) Discussions about different design factors:Unlock Largerfull fractal conduction dimension or a larger total number of branching levels fractal structures (Chen et al., 2015a, 2015b). result in a stronger heat transfer capability and requireWith Free From the experiment point of view, most inves Download Trial less pumping power (Chen and Cheng, 2002), and this experiments only focused on the pressure drop also results in increased temperature uniformity (Wang ture profile of fractal channels (Enfield et al., 200 et al., 2006). Wang et al. (2007) discovered that both the 2007, Chenet al., 2010; Zhang etal.,2013; Xia et pressure drop and the pressure drop change ratio with techniques such as the flow visualization techniq bifurcation angle increase with bifurcation angle,meaning to further investigate the mixing localization and that smaller bifurcation angles are preferred because butionuniformity(Guo et al., 2014). Most of thecur Read Free Foron 30this Days Sign up to vote title whi pressure drop is lower and less sensitive to angle. doesnot utilize flowboiling forthis technique, Useful Not useful needsCancel research (Daniels et al., However, distribution uniformity of the outlet mass flow gap that further anytime. increases as bifurcation angle increases, which results conflictingresults in theliteratureregardingthe pres Special offer for students: Only $4.99/month. in a contradiction if uniform distribution is also a target. This means that the fractal concept alone cannot
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i n t e r n at i o n a l j o u r n al o f r e f r i ge r a t io n 7 8 ( 2 0 1 7 ) 1 – 1 7
Inlet
Inlet
Outlet
Outlet
Fig. 6 – Topology optimized heat sink ( Yaji et a
mimicking lotusleaves (Ensikat et al., 2011; Genzer 2008), and surfaces that reduce drag during moveme mimicking skin of sharks (Bechert et al., 2000). The Fig. 5 – Topology optimized heat sink ( Oevelen and of various surface structures is based on the variab Baelmans, 2014 ). shapes, micro- and nano-structures on the cell su the formation of multicellular structures (Koch and 2009). Much of this research has been done for the liquid-to-gas heat exchangers, which is a research gap and tionof new surface materials with variable wettabi should be investigated. behavior of solid surfaces can be divided into four From the design method point of view, one should note that accordingto static contactangle ( θ c), i.e.superhydroph most design methods were based on scaling laws, but could (when θ c < 10°), hydrophilic surface (when 10° < not necessarily result in optimized design, often leading to You're Reading a Preview drophobic surface (when 90° < θ c < 150°),and superh incomprehensive and unfair comparison. Some researchers surface (when θ c > 150° anda low hysteresisor a lo pointed out that the shape of the bends had an impact on the Unlock full access with a free trial. of less than 10°) (Koch and Barthlott, 2009). performance, especially the pressure drop. The bends with Koch and Barthlott (2009) summarized the dif fillets for the fractal-like microchannel reduced the local faces found in plants. As an example, the leaves of minor pressure losses as compared to that with theDownload 90° bends, With Free Trial diphyllum (Marsileaceae) are hydrophobic. The leav resulting in a lower overall pressure drop (Zhang et al., 2013). sica oleracea are superhydrophobic. The leaves o Haller et al. (2009) also found that T- and L-junctions with odora are hydrophilic, and the leaves of Ruellia de wedges and radii have a lower pressure drop than those with superhydrophilic. 90° bends and joints, but suffered a degradation of heat transWe found that wettability of the heat exchanger s fer as well. However, these design methods of integrating fillets of heat e significant impact upon the performance and scaling law are still limited in regard of topology change. Read Free Foron 30this Days Sign up to vote title proces under condensation, frosting and defrosting In topology optimization, the shape optimization problem Useful Not useful droplets remain Cancel on fin-and-tube surfaces due to surf anytime. becomes a material distribution problem.The boundary of two resulting in bridging between fins which increase Special offer for students: materials, coolantOnly and$4.99/month. solid, may appear and vanish during sure drop, and may lead to reduction in air-side he optimization. Oevelen and Baelmans (2014) applied topology
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i n t e r n at i o n a l j o u r n a l o f r e f r i ge r a t io n 7 8 ( 2 0 1 7) 1 – 1 7
3.2.
Major findings
Different fin types with and without surface treatments have been examined,including plain fins, wavy fins, slit fins, louvered fins, and lanced fins.The most common surface wettability is hydrophilic and hydrophobic, while superhydrophilic and superhydrophobic surfaces are not widely studied. Major findings are: (1) Dry condition: For completely dry surface condition, the hydrophilic and hydrophobic surfaces have a negligible effect on the thermal-hydraulic performance enhancement. No results are available for superhydrophilic and superhydrophobic surfaces. (2) Condensation condition:The research on coated heat exchangers under condensation condition is summarized in Table 5. Most research found that the air-side heat transfer coefficient of hydrophilic surface under wet condition was similar to those of uncoated surface, it might slightly increase (Min et al., 2011) or decrease (Wang et al., 2002). Though hydrophobic surface for plates is reported to have 25% heat transfer improvement (Rainieri et al., 2009), the heat exchanger with hydrophobic surface has a slight degradation in heat transfer (Liu and Jacobi, 2009). This confliction may be due to specific inlet
condition, fin geometry, condensation mode resistance of coating itself. Dependin wettability of the surface and heat excha etries, condensation occurs in three modes: surface with good wettability), dropwise (on poor wettability) and mixed. Thus condens drophilic surfaces is likely to be filmwise w hydrophobic surfaces is likely to be dropwise plain surface, it is believed that the dropw sation has the largest heat transfer coefficie filmwise condensation has the smallest, bec condensation provides an insulating liquid there are two factors that need to be cons The first one is inlet air condition; this det condensation regime of that on uncoat surface. For hydrophilic surface, if condens uncoated heat exchanger is dropwise, then one has a lower heat transfer coefficient 2002), and if condensation on the unco filmwise, the coated one has a higher heat efficient because of the reduction in film th to limited amount of the condensate reta coated surface (Min et al., 2011).The second f exchanger geometry. For a heat exchanger w fins, even though the uncoated heat exchang
You're Reading a Preview Table 5 – Surface wettability’s effects in condensation Unlock fullprocess. access with a free trial. Tube Fin type Contact angle Heat transfer type coefficient* Mimaki, 1987 Wang and Chang, 1998
Round Plain
Download With Free Trial Uncoated; hydrophilic 2–3% improvement coating Uncoated; hydrophilic coating
Round Plain Parallel louver Louver Round Wavy; lanced and louver Uncoated; hydrophilic coating (10°)
and Webb, MasterHong your semester with Scribd 1999 and Jacobi, Round Plain; slit 92° for uncoated; 10° & The Kim New York Times 2000 for coated
Special offerShin for students: $4.99/month. and Ha, Only Round Plain fin with slant ends 2002
Plain discrete fins
θ A =
65°; θ R = 0
No effect
Pressure 40–50% redu 15–40% redu
No effect
15% reducti 45% reduction f Read Free Foron 30this Days Sign up to vote title no effect for lan No effect Reduction Useful Not useful Cancel anytime.
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filmwise condensation, droplet retention for coated ones would sometimes deteriorate the inherent boundary layer.This restarted the effect of the interrupted surface and caused a degradation in heat transfer. Also, the fin pitch may be so small that even with hydrophobic coating, the bridging effect is not reduced significantly if the uncoated heat exchanger has dropwise condensation (Liu and Jacobi, 2009).
higher on the water film than that of the ba On the contrary, the distribution density droplets formed on the surface of a hydrop exchanger is relatively small, resulting in a l density.
Pressure drop of heat exchangers under frost tions largely depends upon the frost layer mass and Its growing rate is determined by the frost developin All research found that the air-side pressure drop for surthe uncoated surface has the largest pressure drop a faces with hydrophilic coating under wet conditions is less than pressure drop increasing rate, followed by superh that of the uncoated surfaces. However, hydrophobic coating surface (Kim and Lee, 2012), and then hydrophobic s increases the air-side pressure drop as compared to unand Lee, 2012), or superhydrophobic surface (Wang e coated surfaces. As discussed above, the hydrophilic coating There is no comparison between performances of heat exchangers will have a very thin and uniform film which bic and superhydrophobic coated heat exchangers reduces the bridging effect in between adjacent fins and tubes; Regarding heat transfer, some research has f however, the hydrophobic coating heat exchanger results in surface treatment had no significant impact on he dropwise condensation which contributes to the bridging effect. (Huang et al., 2009). Some argued that the heat tra When the heat exchanger reaches its steady state, there is ficient decreased due to air blockage, and thermal certain amount of water retained between the fins of heat excaused by the additional frost layer. Under frost changers. Water retention reduces about 50–75% for hydrophilic tions, the heat transfer rate decreases with time b coated heat exchanger (Kim and Jacobi, 2000; Shin and Ha, 2002). the formation and growth of the frost layer. Wang Thus hydrophilic surface is recommended for tight fin found that the heat transfer rate of uncoated heat e spaced heat exchangers under condensation condition. had the fastest decreasing rate, followed by hydro then superhydrophobic coated ones. The heat tra (3) Frosting condition: Here we compare the frost formafor hydrophilic coated surfaces is 33% lower th You'reheat Readingsuperhydrophobic a Preview tion, mass, thickness and density on different coated surfaces at the 40 min exchanger surfaces. Na and Webb (2003) found that the Kim and Lee (2012) found that the heat transf Unlock full access with a free trial. air at the cold surface should be supersaturated in order superhydrophilic coated surfaces was three times for frost nucleation to occur and a low energy surface that of hydrophobic coated surfaces, and it became (high contact angle) requires higher supersaturation of Free hydrophobic Download With Trial coated surfaces within 40 minutes degree for frost nucleation than a high energy surface. Lee, 2012). Thus factors affecting the surface energy all influence the frost formation process, including temperature of cold (4) Defrosting condition: Melting time positiv surfaces, air humidity, air temperature, air velocity, charlates with frost mass and thickness. Thus th acteristics of the surfaces and foreign particles (Na and time for superhydrophobic coated heat e Webb, 2003).This finding well explains why there is frost was found to be the shortest, followed by h Read Free Foron 30this Days Sign up to vote title unco retardation on hydrophobic surfaces (Kim and Lee, 2012). coated heat exchangers, and then the Useful Not useful However, for frost formation on hydrophilic surfaces, Specially, the mechanism of frost layer melt Cancel anytime. there are conflicting results in literature, some redrophobic coated surfaces is that the layer a Special offer for students: Only $4.99/month. search found frost layer grows faster on hydrophilic the fin-and-tube surface melts first, and then
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i n t e r n at i o n a l j o u r n a l o f r e f r i ge r a t io n 7 8 ( 2 0 1 7) 1 – 1 7
defrosting cycle should be long enough to completely dry out the water spread on the hydrophilic surface, otherwise, the hydrophilic capability of the coating would lessen during the second cycle (Huang et al., 2009). Thus superhydrophobic and hydrophobic surfaces show the best anti-frosting performance and defrosting performance, and are recommended for frosting and defrosting conditions.
Air-cooled condenser is most widely used in resid capacity split heat pumps. When the ambient tem creases, larger air velocity is required.Water-cooled are mainly used for heat pumps with large capac usually integrated with a cooling tower to dissipa the ambient air. Water-cooled condensers are esp in situations where the cooling source is located system. One drawback is that this process consu amount of water and needs a large water pump 3.3. Research gap discussion the water. Evaporative condensers are used for no Based on the literature review, the research gap is discussed heat pumps with large capacity to enhance hea as follows: high ambient temperature. The most common m spray or deluge water directly on the surface of con • For condensation condition, not much work has been the air still flows through the tubes at the same tim done to investigate the effect of superhydrophilic and partially evaporates and partially drains to the bo superhydrophobic surfaces on heat transfer and pressure condenser, and is pumped back up to the spray drop. Under condensation conditions, there are conflictpump. Since the coils do not have to be immerged ing results regarding the heat transfer performance of heat and there is no long distance between the conden exchangers with surface treatments, which reveals that the cooling tower, the water amount and pumping po surface type is not the only factor that contributes to the reduced as compared to water-cooled condenser heat transfer performance. Thus, the calculation requires This evaporative condenser is first used in the a general evaluation factor, which can take into account dustry for many years (Collins and Mathews, 1960; various factors, including the inlet condition and heat ex1964) and much research has been done invest changer geometry. transfer and hydraulic performance, including roun • Although plenty of research has been done for heat ex(Facão and Oliveira, 2000; Finlay and McMillan, 197 changers with fin-and-tube surface treatment, there is no and Siwon´ , 1988; Simpson et al., 1974, 1984; Wataru You'resurface Reading and a Preview research regarding the heat exchangers with in-tube elliptical tube banks (Dreyer et al., 1992; Hasa treatments. Limited research has been done to investigate 2004). Different fin types have been studied as Unlocksurface full access with a free trial. the heat transfer and flow pattern in hydrophilic plain fin (Hasan and Sirén, 2003, 2004; Simpson (Derby et al., 2014; Fang et al., 2010) and hydrophobic surface Wataru et al., 1988; Yang and Clark, 1975 ), wavy in microchannels (Chattopadhyay and Usha, 2016; Chen El Trial Haj Assad, 2010), louvered fin (Chen et al Download Withand Free et al., 2014; Derby et al., 2014; Fang et al., 2010 ). However, et al., 2012; Song et al., 2003; Yang and Clark, 1975; the heat exchanger’s performance has different character2012) and perforated fin (Yang and Clark, 1975 istics regarding heat exchanger geometry, flow malResearchers focused on both model developm distribution, and other factors, as observed for air side periments, trying to explain the mechanism of h (requiring deeper investigation). enhancement by adding water spray as compare pena dition and figuring out how much pressure Read Free Foron 30this Days Sign up to vote title and other characteristics are. Here is thesumm Useful Not useful findings. 4. Evaporative condenser Cancel anytime. Special offer for students: Only $4.99/month. (1) Heat transfer performance compared with 4.1. Evaporative cooling in nature
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Song et al., 2003; Wataru et al., 1988 ). However, there is We observed that at higher air velocity also research arguing that this augmentation was mainly drained in the back of the heat exchanger, w due to the formation of liquid film while the contribution drained into the front of the heat exchange of evaporation was rather negligible (Yang and Clark, velocity was low. The percentage of draina 1975). Yang and Clark observed that the sprays of water creased as more water sprayed (Zhang et al (evaporates at 100°C, C p 4.2 kJ kg 1 K 1 ) and ethylene (7) Inlet air RH: In a humid and hot environmen glycol (evaporates at 197°C, C p 3.1 kJ kg 1 K 1) yielded inlet air relative humidity may restrain the same results. But this comparison cannot necessarily tion of water drops, resulting in performanc indicate that the contribution of evaporation is not sigIt was found that the water accumulation ap nificant. Lang and Bergles (1996) found the sum of air inlet air humidity was 80%, but we did not ob and water heat rate did not equal to that of the heat exwhen inlet air humidity was only 40%. The h changer capacity, thus one can draw the conclusion that hancement ratios reduced from 4.1 to 2.8 removing sensible heat alone could not be the reason humidity increased from 40% to 80%, and t for heat transfer enhancement of spray cooling. penalty increased from 0% to 25% respectiv (3) Pressure drop: Most research found the pressure penalty, 2013). Thus, we recommend an evaporative if there was one, to be insignificant for spray cooling for dry and hot environments. (Chen et al., 2013; Simpson et al., 1984; Wataru et al., 1988; (8) Dry out phenomenon: At low spray water rat Yang and Clark, 1975; Zhang et al., 2012). However, Dreyer of tube-and-fin might remain dry (Simpson e (1992) pointed out that pressure drop was related to fin and dry out pattern was affected by air flow r spacing, and it should not be neglected when fin spacing water rate and surface temperature. was smaller than 2.5 mm. Popli et al. (2012) found that (9) System performance: Much research has bee at same air velocity (1.4 m/s), the pressure of deluge vestigating the performance of evaporative c cooling was about 2.3 times of that under dry conditions in a vapor compression cycle, and other cooli and the capacity was about 2.7 times of that under dry and were reviewed by Harby et al. (2016). They conditions. Chen et al. (2013) experimentally found similar by using evaporative condenser, the power pressure jump at low air flow rate (Re = 100–250) when tion could be reduced up to 58% and the coe You're a Preview spray rate was high and also pointed out high inletReading air performance could be improved by 113.4% wi humidity led to a pressure drop penalty as well. of different cooling capacities ranging from 3 t Unlock full access with a free trial. with an air-cooled condenser. (4) Fin design: Traditional long thin fins can significantly compared improve heat transfer under dry conditions; however, (10) Drawbacks and new designs: Despite the ben Dreyer (1992) found that the fin efficiencyDownload decreased With Free areTrial certain drawbacks from evaporative co under wet conditions because of the high heat transfer For instance, fouling issues and power con coefficient on air side, which could be as low as 43% (pumping and fan) are drawbacks.Finlay and (Hasan and Sirén, 2003). Highest enhancement ratios pointed out that such condensers had vulne were observed for geometries with low fin heights and fouling. Fouling had been observed at the w wide fin spacing (Simpson et al., 1974).Thus Dreyer et al. faces on a louvered fin heat exchanger after tw time o (1992) and Song et al. (2003) recommended short and on-and-off spray testing (with spray Read Free Foron 30this Days Sign up to vote title thick fin designs to take full advantage of the evapora100 hours) using tap water. The fouling p Useful Not useful from tive cooling. Furthermore, due to the blockage in low fin sulted the position and orientation of Cancel anytime. spacing cases, we recommend that fin spacing be wider (Zhang et al., 2012). Although the pumpin Special offer for students: Only $4.99/month. than 3 or 4 mm apart. smaller for an evaporative condenser as com =
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13 times larger than the air-cooler condenser at the same conditions. 4.3.
Research gaps
Here is the discussion of research gap regarding evaporative condenser.
• Spray pattern optimization. Water, as an important resource, can be rare and precious, especially in hot and dry areas where an evaporative condenser is highly applicable. Thus it is urgent to optimize the spray pattern and take into account nozzle shape, water spray rate, spray orientation, and spray pattern to minimize water consumption. • Water blockage and pressure penalty. Most research did not find pressure penalty because the coils that had been examined were mainly bare tube bundles, or plain fin-andtube heat exchangers. However,when fin geometry becomes complex and fin spacing becomes smaller, water blockage and the pressure drop penalty would become an issue. More research should be done in order to fully understand the limitations. • Universal condenser design and optimization for both dry and wet conditions. To save water and protect the system, condensers may need to run under dry conditions for most of the time, and rununder wet conditionin extreme weather. You're Reading a Preview Based upon the review it is clear that the heat exchanger that has been optimized in dry conditions may suffer a Fig.a 7free – Approach for applying biomimicry to he Unlock full access with trial. pressure drop penalty when used as evaporative conexchanger design. denser. Thus, a universal condenser design that can have good performance in both conditions should beDownload investigated.With Free Trial • Performance of condenser with hydrophobic and hydromade and further analysis should be done to inv philic coating. There is no sufficient research studying performance of the design. Analysis includes an the effect of spray cooling on coated heat exchangers. The merical analysis, optimization, manufacturin coating may be a solution for universal condenser design. checking, and prototype manufacturing and ex • Innovative designs. To reduce the pumping power and fan investigation. power, innovative designs should be looked to find an acFree Foron 30 Days Sign to vote this title HereRead is anup illustration of this procedure by us ceptable way to utilize less water. fractal heat sink design as an example: Useful useful Not
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• Define problem and requirements: Design a he
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principles that have the potential to be utilized in heat exchanger design. Here is a brief discussion about these phenomena and principles.
and evaporative condensers are inspired by sweating skins.We critically reviewed all of these technologi and have proposed an approach to apply biomimi exchanger design. We have discussed promising na nomena that have not yet been applied to the heat design, such as thermal regulation control mecha ficial skin materials, fish body shapes, shark skin vibration. This review is expected to throw a lig future research of nature-inspired heat and mas devices.
• Control mechanism of sweating can be used for spray cooling pattern design and control. Humans have developed a meticulous control system for thermoregulation. Even though evaporative condensers utilize the idea of evaporation of human skins, there is no research of the spray pattern design and control. The spray pattern should be controlled based upon the ambient temperature, the coil temperature, the ambient humidity, air flow rate and other parameters. This may lead to least amount of water consumption. Acknowledgements • Artificial skin materials can be used as a heat exchanger coating to replace spray cooling and to save pumping power. Recently, a novel passive cooling solution using temperatureThe authors gratefully acknowledge the support of sensitive hydrogel (TSHG), a smart macromolecular material from the Center for Environmental Energy Engine which is capable of releasing moisture automatically when versity of Maryland, CEEE, UMD. its temperature exceeds the lower critical solution transition temperature, has been applied to microelectronics devices (Cui et al., 2014; Huang et al., 2012). This solution REFERENCES was found to achieve 4.9 times higher cooling capacity than traditional passive cooling limits (Huang et al., 2012). This technology requires no fan power or pumping power. Alharbi, A.Y., Pence, D.V., Cullion, R.N., 2003. Fluid flow • Fish body shapes can be used to design tube shape of heat microscale fractal-like branching channel network exchangers. In literature, research has been conducted on Eng. 125 (6), 1051. http://doi.org/10.1115/1.1625684 You're a Preview Alharbi, A.Y., Pence, D.V., Cullion, R.N., 2004. Thermal mostly round tubes and oval tubes. Round tubes have Reading the characteristics of microscale fractal-like branching advantage of holding high pressure inside. However, to channels. J. Heat Transfer 126 (5), 744. http://doi.org Unlock tubes full access with a free trial. reduce the air-side pressure drop, streamline shaped 1.1795236. should be further investigated. Azad, A.V., Amidpour, M., 2011. Economic optimization • Shark skin can be used to design low friction tube coating. With Free and tube heat exchanger based on constructal theo Download Trial Shark skin has low drag, which enables sharks to swim more 36 (2), 1087–1096. ISSN 0360-5442. smoothly through water. A new film has been developed and Bacellar, D., Aute, V., Huang, Z., Radermacher, R. 2016. N airside heat transfer surface designs using an integ applied to coat the blades of wind turbines and vehicles multi-scale analysis with topology and shape optim (Salaverry, 2012) mimicking the shark skin design and leading International Refrigeration and Air Conditioning Co to efficiency enhancement. This approach may be used in West Lafayette. Paper 2117. heat exchangers to reduce the fan power. Bechert, D.W., Hage, W., Meyer, Read Free For 30this Days SignBruse, up to M., vote on title R., 2000. Fluid • Vibration of wings inspired fan integrated heat exchangmechanics of biological surfaces and their technolo Not useful87 (4), 157–171. Useful ers. Powers et al. (2015) found that a hummingbird dissipated application. Naturwissenschaften Cancel anytime. http://doi.org/10.1007/s001140050696. through convection around the wings during hovSpecial offerits forheat students: Only $4.99/month. Bejan, A., 1997. Constructal-theory network of conduc ering.The fast-flapping wings dissipate the heat efficiently
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Chattopadhyay, G., Usha, R., 2016. On the Yih–Marangoni Facão, J., Oliveira, A.C., 2000. Thermal behaviour of instability of a two-phase plane Poiseuille flow in a cooling towers for use with chilled ceilings. Appl. hydrophobic channel. Chem. Eng. Sci. 145, 214–232. 20 (13), 1225–1236. http://doi.org/10.1016/S1359 -4311(99)00096-4. http://doi.org/10.1016/j.ces.2016.02.012. Chen, C.-W., Yang, C.-Y., Hu, Y.-T., 2013. Heat transfer Fang, C., David, M., Wang, F., Goodson, K.E., 2010. Influ enhancement of spray cooling on flat aluminum tube heat of film thickness and cross-sectional geometry on exchanger. Heat Transfer Eng. 34 (1), 29–36. http://doi.org/ hydrophilic microchannel condensation. Int. J. 10.1080/01457632.2013.694742. 36 (8), 608–619. http://doi.org/10.1016/j.ijmultipha Chen, Y., Cheng, P., 2002. Heat transfer and pressure drop in .2010.04.005. fractal tree-like microchannel nets. Int. J. Heat Mass Finlay, I.C., Harris, D., 1984. Evaporative cooling of Transf. 45 (13), 2643–2648. http://doi.org/10.1016/S0017 Int. J. Refrigeration 7 (4), 214–224. http://doi.org/10 -9310(02)00013-3. 0140-7007(84)90073-2. Chen, Y., Zhang, C., Shi, M., Yang, Y., 2010. Thermal and Finlay, I.C., McMillan, T. 1970. Pressure drop, heat tran hydrodynamic characteristics of constructal tree-shaped gas-liquid mist, ASME IHTC, Jerusalem, KN-29,445 minichannel heat sink. AIChE J. 56 (8), 2018–2029. Genzer, J., Marmur, A., 2008. Biological and synthetic http://doi.org/10.1002/aic. cleaning surfaces. MRS Bull. 33, 742–746. http://do Chen, Y., Zhang, C., Wu, R., Shi, M., 2011. Methanol steam http://dx.doi.org/10.1557/mrs2008.159. reforming in microreactor with constructal tree-shaped Guo, X., Fan, Y., Luo, L., 2014. Multi-channel heat exch network. J. Power Sources 196 (15), 6366–6373. reactor using arborescent distributors: a characte http://doi.org/10.1016/j.jpowsour.2011.03.044. study of fluid distribution, heat exchange perform Chen, Y., Chaoqun, S., Shi, M., Peterson George, P., 2014. Modeling exothermic reaction. Energy 69, 728–741. http://do and simulation of the polymeric nanocapsule formation 10.1016/j.energy.2014.03.069 . process. AIChE J. 60 (3), 1182–1192. http://doi.org/10.1002/aic. Haller, D., Woias, P., Kockmann, N., 2009. Simulation a Chen, Y., Deng, Z., Cheng, Q., 2015a. Thermal conductivity of Si/ experimental investigation of pressure loss and h Ge nanocomposites with fractal tree-shaped networks by in microchannel networks containing bends and considering the phonon interface scattering. Int. J. Heat Mass Int. J. Heat Mass Transf. 52 (11–12), 2678–2689. htt Transf. 88, 572–578. http://doi.org/10.1016/j.ijheatmasstransfer 10.1016/j.ijheatmasstransfer.2008.09.042. .2015.04.093. Harby, K., Gebaly, D.R., Koura, N.S., Hassan, M.S., 2016 Chen, Y., Yao, F., Huang, X., 2015b. Mass transfer and reaction in Performance improvement of vapor compression methanol steam reforming reactor with fractal tree-like systems using evaporative condenser: an overvie You're Reading a Preview microchannel network. Int. J. Heat Mass Transf. 87, 279–283. Sustain. Energy Rev. 58, 347–360. http://doi.org/10 http://doi.org/10.1016/j.ijheatmasstransfer.2015.04.006. j.rser.2015.12.313. Collins, G.E., Mathews, R.T., 1960. Improving air-cooler design. Harris, L.S., 1962. For flexibility, the air-evaporative co Unlock full access with a free trial. Cherm. Eng. 137–142. Eng. 77–82. Cui, S., Hu, Y., Huang, Z., Ma, C., Yu, L., Hu, X., 2014. Cooling Harris, L.S. 1964. Let’s look at the new wetted-fin com performance of bio-mimic perspiration by temperatureair-evaporative cooler, Power, 65–67. Download With Free Trial sensitive hydrogel. Int. J.Therm. Sci. 79, 276–282. Hasan, A., Sirén, K., 2003. Performance investigation http://doi.org/10.1016/j.ijthermalsci.2014.01.015. finned tube evaporatively cooled heat exchangers Daniels, B., Liburdy, J.A., Pence, D.V., 2007. Adiabatic flow boiling Therm. Eng. 23 (3), 325–340. http://doi.org/10.10 in fractal-like microchannels. Heat Transfer Eng. 28 (10), 817– j.applthermaleng.2003.10.022. 825. http://doi.org/10.1080/01457630701378218 . Hasan, A., Sirén, K., 2004. Performance investigation Daniels, B.J., Liburdy, J.A., Pence, D.V., 2011. Experimental studies circular and oval tube evaporatively cooled heat e Free For 30this Days of adiabatic flow boiling in fractal-like branching Appl.Read Therm. Eng. 24 (5–6), 777–790. Sign up to vote on title http://doi.org microchannels. Exp. Therm. Fluid Sci. 35 (1), 1–10. j.applthermaleng.2003.10.022. Useful Not useful Cheng, H., Joo, G.T., 2007. Conjugate h http://doi.org/10.1016/j.expthermflusci.2010.07.016. Hong, F.J., P., Ge, Cancel anytime. Derby, M.M., Chatterjee, A., Peles, Y., Jensen, M.K., 2014. Flow in fractal-shaped microchannel network heat sin Special offer for students: Only $4.99/month. condensation heat transfer enhancement in a mini-channel integrated microelectronic cooling application. In
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Jhee, S., Lee, K.S., Kim, W.S., 2002. Effect of surface treatments on United States of America (Vol. 12, pp. 207–214). http the frosting/defrosting behavior of a fin-tube heat exchanger. 10.1085/jgp.9.6.835. Int. J. Refrigeration 25 (8), 1047–1053. http://doi.org/10.1016/ Na, B., Webb, R.L., 2003. A fundamental understanding affecting frost nucleation. Int. J. Heat Mass Transf. 4 S0140-7007(02)00008-7. Kim, G.J., Jacobi, A.M. 2000. Condensate accumulation effects on 3797–3808. http://dx.doi.org/10.1016/S0017-9310 the air-side thermal performance of slit-fin surfaces, ISSN 0017-9310. 61801(217). http://hdl.handle.net/2142/13333. (Accessed 31 Nasr, M.M., Hassan, M.S., 2009. Experimental and theor July 2009). investigation of an innovative evaporative condens Kim, K., Lee, K.S., 2012. Characteristics and performance residential refrigerator. Renew Energy 34 (11), 2447– evaluation of surface-treated louvered-fin heat exchangers http://doi.org/10.1016/j.renene.2009.03.008. under frosting and wet conditions. Int. J. Heat Mass Transf. 55 Oevelen, T.V., Baelmans, M. 2014. Numerical topology (23–24), 6676–6681. http://doi.org/10.1016/j.ijheatmasstransfer optimization of heat sinks. Proceedings of the 15th .2012.06.076. International Heat Transfer Conference, 1-15. http: Koch, K., Barthlott, W., 2009. Superhydrophobic and 10.1615/ihtc15.opt.009168. superhydrophilic plant surfaces: an inspiration for Pawlowski, M., Siwon´ , B., 1988. Heat transfer between g biomimetic materials. Philos.Trans. A Math. Phys. Eng. Sci. spray stream flowing perpendicularly to the row of 367 (1893), 1487–1509. http://doi.org/10.1098/rsta.2009.0022. cylinders. Wärme- Und Stoffübertragung 22 (1–2), 9 Koplow, J.P. 2010. A fundamentally new approach to air-cooled http://doi.org/10.1007/BF01001578. heat exchangers. Sandia National Lab. Pence, D.V., 2002. Reduced pumping power and wall te Lang, S.K., Bergles, A.E., 1996. The effects of water spray in microchannel heat sinks with fractal-like branch cooling on cooler performance. Chem. Eng. Commun. 153-153, channel networks. Microsc. Therm. Eng. 6 (3), 319–3 231–252. Popli, S., Hwang, Y., Radermacher, R. 2012. Enhanceme Liang, C., Wang, F., Lü, Y., Wu, C., Zhang, X., Zhang, Y., 2015. tube-louver fin heat exchanger performance using Experimental study of the effects of fin surface water cooling. International Refrigeration and Air characteristics on defrosting behavior. Appl. Therm. Conditioning Conference (1973), 1–10. Eng. 75, 86–92. http://doi.org/10.1016/j.applthermaleng Powers, D.R., Tobalske, B.W., Wilson, J.K., Woods, H.A., C .2014.09.082. K.R., 2015. Heat dissipation during hovering and for Liu, L., Jacobi, A.M., 2009. Air-side surface wettability effects on flight in hummingbirds. Proc. Royal Soc. B http://do the performance of slit-fin-and-tube heat exchangers 10.1098/rsos.150598. operating under wet-surface conditions. J. Heat Transfer 131 Rainieri, S., Bozzoli, F., Pagliarini, G., 2009. Effect of a You're Reading ahydrophobic Preview coating on the local heat transfer coef (5), 051802. http://doi.org/10.1115/1.2994722. Liu, Z., Wang, H., Zhang, X., Meng, S., Ma, C., 2006. An in forced convection under wet conditions. Exp. He experimental study on minimizing frost deposition on a full coldaccess withTransf. 22 (3), 163–177. http://doi.org/10.1080/ Unlock a free trial. surface under natural convection conditions by use of a novel 08916150902950004. anti-frosting paint. Part I. Anti-frosting performance and Salaverry, P. 2012. Method of reducing drag on other su comparison with the uncoated metallic surface. Int. J. vehicle. J. Adv. Eng. Res. 3 (1), 26–32. ISSN: 2393-8447 Download With Free Trial Refrigeration 29 (2), 229–236. http://dx.doi.org/10.1016/j.ijrefrig Senn, S.M., Poulikakos, D., 2004. Laminar mixing, heat .2005.05.018. ISSN 0140-7007. and pressure drop in tree-like microchannel nets a Liu, Z., Gou, Y., Wang, J., Cheng, S., 2008. Frost formation on a application for thermal management in polymer el super-hydrophobic surface under natural convection fuel cells. J. Power Sources 130 (1–2), 178–191. http:/ conditions. Int. J. Heat Mass Transf. 51 (25–26), 5975–5982. 10.1016/j.jpowsour.2003.12.025. http://dx.doi.org/10.1016/j.ijheatmasstransfer.2008.03.026. Sherman, T.F., 1981. On connecting large vessels to Read Free For 30 Days ISSN 0017-9310. meaning of up Murray’s law. J.this Gen. Physiol. 78 (4), 431 Sign to vote on title Luo, L., Fan, Y., Zhang, W., Yuan, X., Midoux, N., 2007. Integration http://doi.org/10.1085/jgp.78.4.431. Useful Not useful S., 2002. of constructal distributors to a mini crossflow heat Shin, J., Ha, Theanytime. effect of hydrophilicity on con Cancel and their configuration optimization. over various types of fin-and-tube heat exchangers Special offerexchanger for students: Only assembly $4.99/month. Chem. Eng. Sci. 62 (13), 3605–3619. http://doi.org/10.1016/ Refrigeration 25 (6), 688–694. http://doi.org/10.101
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i n t e r n at i o n a l j o u r n a l o f r e f r i ge r a t io n 7 8 ( 2 0 1 7) 1 – 1 7
Staats, W.L., Brisson, J.G., 2015. Active heat transfer enhancement Xia, C., Fu, J., Lai, J., Yao, X., Chen, Z., 2015. Conjugate in air cooled heat sinks using integrated centrifugal fans. Int. transfer in fractal tree-like channels network hea J. Heat Mass Transf. 82, 189–205. http://doi.org/10.1016/ high-speed motorized spindle cooling. Appl. Ther 1032–1042. http://doi.org/10.1016/j.applthermalen j.ijheatmasstransfer.2014.10.075. Tavsan, C., Tavsan, F., Sonmez, E., 2015. Biomimicry in .07.024. architectural design education. Procedia Soc. Behav. Sci. 182, Xu, P., Yu, B., 2006. The scaling laws of transport prop 489–496. http://doi.org/10.1016/j.sbspro.2015.04.832. fractal-like tree networks. J. Appl. Phys. 100 (10), Tondeur, D., Luo, L., 2004. Design and sc aling laws of ramified 10.1063/1.2392935. fluid distributors by the constructal approach. Chem. Eng. 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Heat and mass transfer and mass transfer to air from a compact heat exc Cancel anytime. analysis of a wavy heat exchanger under fully water spray precooling and surface deluge coolin Special offer for students: Onlyfin-and-tube $4.99/month. and partially wet surface conditions. Int. J. Therm. Sci. 49 (2), Therm. Eng. 63 (2), 528–540. http://doi.org/10.10
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