Temperature Control by Heat Exchanger Incorporating with Vibration Type Coiled-tube

Transcription

1 emperature Control by Heat Exchanger Incorporating with Vibration ype Coiled-tube A. haikua a, P. Kittiupakorn a*, S. anthadiloke a Abtract - In a hard chrome electroplating proce, a heat exchanger i employed to remove the heat produced from high current load and heat of reaction involved in an electroplating tank to maintain an optimal temperature of the plating olution in the range of C. If the temperature of plating olution in the electroplating tank i higher than the pecified temperature, the metal depoit will become white and milky burning quickly on the edge and the phyical propertie are deteriorated. hi i becaue in the everal plant an original 2 U-hape tube heat exchanger cannot provide inufficiently heat removed out of the electroplating tank. hi rk i aimed at tudying alternative deign to enhance the heat tranfer rate which coil are inerted into the tube and flow-induced vibration i introduced. In addition, to evaluate the effectivene of the new deign heat exchanger, it mathematical model with unknown parameter (i.e. overall heat tranfer coefficient, total lo factor) ha been developed baed on actual plant data. he experimental and imulation reult have hown that the implementation of the new deign tructure with the diameter of 1 inch and the length of meter can maintain the optimal temperature. hu, the new deign heat exchanger i applicable to employ in a real continuou hard chrome plating proce; the overall heat tranfer coefficient i increaed about 10% and correponding to the production of 9.7% per year without any lot regarding to over temperature. Index erm - flow-induced vibration, coil inerted, tube heat exchanger, hard chrome I. INRODUCIONS Hard chrome electroplating or functional chrome plating, i a chromium coating proce to enhance a thickne and endurance of a rk piece. o enhance the thickne of chromium coating procedure i generally in between micron or more. he factor that affect the efficiency of the finihed rk piece include operating condition uch a a concentration of chromic acid, ulfuric acid, the voltage and current requirement [1,2,3]. In addition, temperature of chromic acid olution i a main variable factor defective caue on rk-piece urface. Motly, the major problem in hard chrome electroplating manufactory in hailand i the continuou increae in the temperature of plating olution until over it temperature all wate. Generally, the heat exchanger i ued to remove the heat which i produced from high current load in the electroplating proce. Author are grateful thank to hailand reearch Fund (RF) under he RF-Mater reearch grant program for financial upport contract number: MRG545E003 and Siam Hard Chrome Co., Ltd for information, proce equipment upport during the reearch. a Department of Chemical Engineering, Chulalongkorn Univerity, Bangkok, hailand (*correponding author Paian.k@chula.ac.th, Paian_cu@hotmail.com) he appropriate temperature of planting olution i between 47 and 53 C [2,3,4], that will create the tandard quality of rk. hu, developing the capacity of heat exchanger i an important factor to conitently retain pecific range of temperature of plating olution. he performance of heat exchanger can be improved to perform a certain heat tranfer duty by heat tranfer enhancement technique. Wong-wie and Naphon[4] propoed the review of flow and heat tranfer characteritic in curved pipe including the heat tranfer coefficient in ingle-phae and friction factor in inglephae and t-phae. Ref. [3-7] invetigated the dynamic characteritic of curved pipe conveying fluid by everal method. he equation of motion are preented with the fluid velocity. he effect of ome key parameter on the natural frequency on the pipe ytem are alo hown by their olution. Ref. [8-12] propoed the effect of tranvere vibration on free convection from a horizontal cylinder. hey reported that a coniderable increae the heat tranfer coefficient wa obtained with vibration. Cheng and Luan et al. [12] deigned the new tructure of heat tranfer device which can freely vibrate under the influence of fluid flow. hey found that the vibration induced by the pulation flow at the low flow velocity can ignificantly increae the convective heat tranfer coefficient of the nonlinear heat tranfer device. For the econd technique coil inerted into a flow provide wirling flow of the boundary layer, increae the effective heat tranfer area and the turbulence intenity. he wirl induced tangential flow velocity component caue improved fluid mixing between the tube core and the wall region nearby. hu, Enhancing of the heat tranfer by rapid fluid mixing [13]. Ref. [13-18] preented the ue of coil inert to pipe/tube leading to a coniderable increae in heat tranfer. hey are reported that a coniderable increae the heat tranfer coefficient wa depend on the Reynold number of fluid flow, coiled pitch ratio and coiled diameter. hi rk preent a new approach to enhance the heat tranfer rate by the flow-induced vibration, inert coiled into the tube of the heat exchanger and contructed in a real plant. Mathematical model wa created to repreent thi ytem. he better of dynamic equation ha been developed by the parameter from optimization method and it can determined the correct value of the overall heat tranfer coefficient that caue the temperature of the plating olution out of the range. II. HE NEW DESIGN SRUCURE he eence of vibration i the mechanical energy continuouly accumulate and diipate. he medium flow in the heat exchanger may caue the energy build-up due to the fluid vicoity. herefore, it i almot impoible to completely avoid the vibration of the heat tranfer device. In fact, a weak vibration of the heat tranfer device alway

2 occur when the fluid flow in curved pipe. he decribe cae include water-hammer, turbulence-induced vibration, partial-flow regime, pump noie, pulating flow etc. In the preent rk we attempt to create a new type of tube heat exchanger which can vibrate under the influence of the fluid flow. he original tube heat exchanger wa deigned in normal characteritic 2 piece of U-tube which i immered along the height of electroplating tank. he new deign tructure i different from the conventional one ued in a real plant. he characteritic of thi device i curved tube which are jointed by the traight tube with 30 o of depreing angle. he main body conit of four circular titanium tube a hown in Figure 1. paed the cooling proce will be torage in the cooling water tank again. After that the cooling water ha pumped to the coiled-tube heat exchanger. Fig. 2 A cooling ytem for a hard chrome plating proce. Fig. 1 he front/ide view of the new deign tructure he freely vibrate occur at the bottom of circular tube when the fluid flow through the curved tructure. Moreover, inide the titanium tube i added the titanium pring along the curved tube for increae the faying urface between cooling water and circular titanium tube. III. MAHEMAICAL MODEL A proce tudied in thi rk conit of an electroplating tank, a how a Figure 2. Let denote the temperature and Q denote the energy rate. he heat tranfer between the electroplating tank i connected with a cooling ytem can be decribed that the heat produced from the electrical load i removed by an internal heat tranfer coil. Starting with the water flow rate, F w with temperature, win i flowed through the internal coiled-tube heat exchanger immered in the plating olution, with have the temperature. At that time, the heat i tranferred from the plating olution to raie the water temperature in the coiled-tube up with temperature, ut. he water left out of the electroplating tank i tranferred to the cooling water tank. he water from the cooling water tank ha pumped a input of the cooling tower and output of cooling water which i For thi tudy, the ma conervation model are developed under the teady tate condition wherea the energy conervation equation are derived bae on the dynamic condition of the actual plant data. he energy conervation model of the electroplating tank are compoed of energy input (power input), the heat tranferring of the coiled-tube heat exchanger and the heat lo to urrounding. he energy conervation of the electroplating tank and internal coiled-tube heat exchanger are: U A d o ht lm Qlo F (1) dt VCp d Fw wi U o Aht lm (2) dt Ao L wcpw Ao L ( wi ) ( ) Where lm (3) ( wi) ln ( ). RESULS AND DISCUSSIONS he aim of multi-objective optimization i determined the unknown parameter in eq. (1) uch a overall heat tranfer coefficient (U o ) and total lo factor (F ). hi ection provided for comparion the performance of the heat exchanger between the original and a vibration type coiledtube heat exchanger (new deign). Aumption made regarding the development of the model are: - the phyical propertie, denity, heat capacity of the plating olution and the water to be contant in the temperature range, - the volume of the plating olution in the electroplating tank i aumed contant,

3 - the temperature water in the internal tube heat exchanger i linearly change with the ditance in the flow direction. And the heat tranfer between air and the coil outide the electroplating tank i neglected, Referring to the model developed, an unknown parameter uch a an overall heat tranfer coefficient baed on the heat exchanger area (U o ) and total lo factor (F ) needed to be determined. he randomized 2 batch ampling of the electroplating proce were conidered to imulate the overall heat tranfer coefficient (U o ) and the total lo factor (F ) from the actual plant data. he property of fluid and the parameter of unit are preented in able 1 and the initial value of the variable i given in able 2 for the electroplating proce batch 1, 2, 5, 6 repectively ABLE 1 NOMINAL VALUES FOR HE PROCESS PARAMEERS 1,174.4 kg/m kg/m 3 w Cp 4.18 kj/kg C w V 7.0 m 3 Ao ( Coiled ube) o( U ube) 1.58 m 2 A 0.96 m 2 mw m 2 ABLE 2: HE INIIAL VALUE OF VARIABLES U-ube Heat Exchanger Coiled-ube Heat Exchanger Batch 1 Batch 2 Batch 5 Batch C C 2.5 x C C 2.5 x C C 3.5 x C C 3.2 x 5.5 Fig. 3 he temperature profile of the plating olution and the water out with actual plant data of the U-tube heat exchanger batch 1 and 2.

4 Fig. 4 he temperature profile of the plating olution and the water out with actual plant data of a vibration type coiled-tube heat exchanger batch 5 and 6. he actual plant data wa ued to find the value of overall heat tranfer coefficient (U o ) and total lo factor (F ) for heat tranferring both type of the heat exchanger. he imulation reult were compared with the actual plant data. he imulation reult of batch 1 and 2 were preented in the figure 3 and the plating olution temperature profile varied with time wa accurately fitted with the actual data. At the beginning of both batche, the plating olution temperature tended to increae due to heat generated by the high electric current, then the plating olution temperature continuou increaed over the optimal temperature range in the batch 2 (econd batch in ucceive operation). he figure 4 howed the imulation reult of batch 5 and 6, the plating olution temperature varied with time wa fitted with the actual data. In the econd batch (batch 6) after the firt batch, it wa found that the plating olution temperature lightly increaed but remained within the optimal temperature range (47-53 C). On the figure 3 and 4, the trend of the cooling water out temperature from imulation wa fitted with the collected data (red dot) and lightly increaed. he behavior in the term of the heat generated by the value wa changed a tep change. At the beginning of the plating proce (0-30 min), the value of wa adjuted higher than the operating etting value to induced chromium to hold all area of rk piece. hen it wa tuned by actual data. he determined value of the overall heat tranfer coefficient (U o ) and the total lo factor (F ) by the multiobjective optimization method were given in table 3. able 3: he correct value of U o and F Batch U 0 (Watt/m 2 C) Parameter F ( C/ec) ISE V. CONCLUSION According to the ucce reult of A vibration type coiled tube heat exchanger experimentation how it capacity of maintaining the pecific temperature range of plating olution, which i C. hi new deign heat exchanger can provide high heat tranfer rate reulting in the overall heat tranfer coefficient of W/m 2 C comparing to the overall heat tranfer coefficient of W/m 2 C of the original machine. hi tet prove that the new heat exchanger capacity in an overall heat tranfer coefficient can be increaed about 10%. In ummary, the calculated total lo factor (F ) are and C/ec for original and new heat exchanger repectively. he imulation reult have hown that the developed model give a good of the plating olution temperature with mall

5 error. In addition, the new deign tube heat exchanger i applicable to employ in the real continuou hard chrome plating proce and correponding to the production of 9.7% per year. REFERENCES [1] Greenod, J.D. (1971).Hard chrome plating. Second edition.eddington: Robert Draper. [2] Boriboonri, P.Study of dynamic behavior of heat exchanger ytem in hard chrome electroplating, hei for Mater Degree of Chemical EngineeringChulalongkorn Univerity, [3] Kongthep, A. Deign of a flow-induced vibrating tube heat exchanger for a hard chrome plating proce, hei for Mater Degree of Chemical EngineeringChulalongkorn Univerity, [4] P. Naphon, S. Wongwie, A review of flow and heat tranfer characteritic in curved tube. Renerwable & Sutainable Energy Review. 10(2006), pp [5] Lin, N. Qiao. In plan vibration analye of curved pipe conveying fluid uing the generalized differential quadrature rule.computer and tructure. 86(2008), pp [6] D. Jung, J. Chung. Dynamic tability of a emi-circular pipe conveying harmonically ocillating fluid.journal of Sound and Vibration. 315(2008), pp [7] D. Jung, J. Chung. A teady-tate equilibrium configuration in the dynamic analyi of a curved pipe conveying fluid.journal of Sund and Vibration. 294(2006), pp [7] A.S. [8] Daod, B.L. Manocha and S.M.J. Ali. he effect of vertical vibration on natural convection heat tranfer from a horizontal cylinder.int. J. Heat Ma ranfer. 24(1981),pp [9] R. Lemlich, M.A. Rao. he effect of tranvere vibration on free convection from a horizontal cylinder. Int. J. Heat Ma ranfer.8(1965), pp [10] A.S. Daod, B.L. Manocha and S.M.J. Ali. he effect of vertical vibration on natural convection heat tranfer from a horizontal cylinder.int. J. Heat Ma ranfer. 24(1981),pp [11] Y.H. Lee, D.H. Kim and S.H. Chang. An experimental invetigation on the critical heat flux enhancement by mechanical vibration in vertiacal round tube.nucl.eng. De. 229(2004),pp [12] Cheng L., Luan., and Xu W.D.M. Heat tranfer enhancement by flow-induced vibration in heat exchanger.international Journal of Heat and Ma ranfer 52(2009): [13] S. Gune, V. Ozceyhan, and Orhan B. Heat tranfer enhancement in tube with equilateral triangle cro ectioned coiled wire inert. Experimental hermal and Fluid Science. 34(2010): [14] S. Gune, V. Ozceyhan, he experimental invetigation of heat tranfer and preure drop in atube with coiled wire inert placed eparately from the tube wall. Applied hermal Engineering. 30 (2010): [15] A. Garcia, P. G. Vicente. Experimental tudy of heat tranfer enhancement with wire coil inert In laminar-tranition-turbulent regime at different Prandtl number. International Journal ofheat and Ma ranfer. 48 (2005): [16] A. Garcia, J. P. Solano, Enhancement of laminar and tranitional flow heat tranfer in tube by mean of wire coil inert. International Journal of Heat and Ma ranfer. 50 (2007): [17] A. Zachar., Analyi of coiled-tube heat exchanger to improve heat tranfer rate with pirally corrugated wall. International Journal of Heat and Ma tranfer. 53 (2010): [18] Prabhanjan, D.G., and Paghavan, G. S. V., Comparion of heat tranfer rate between a traight tube heat exchanger and a helically coiled heat exchanger. International Journal of Heatand Ma ranfer. 29 (2002):