1 Performance and Cost

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1 Pefomance and Cost Analysis and Reseach of Ai-Cooled Using Small Diamete Coppe Tubes Wu Yang, Li Changsheng and Deng Bin Abstact Replacing coppe tubes with aluminum tubes and using coppe tubes with smalle tube diametes ae the two popula tends cuently to lowe the cost of ai conditiones. This epot appoaches fom the pespective of using coppe tubes with smalle tube diametes as a substitution. Pefomance compaison as well as cost analysis ae conducted fo the two tube types of Φ9.52mm inne-gooved coppe tube and Φ5mm inne-gooved coppe tube, as well as the heat exchanges using these two tube types. The eseach esults show that: whee the expeimental conditions and volume flow ae the same, the heat exchange coefficient within the Φ5mm inne-gooved coppe tube is about 15% highe than that within the Φ9.52mm inne-gooved coppe tube. Whee the testing opeating conditions and the windwad dimensions ae the same, when the Φ5mm coppe tube heat exchange has achieved a simila heat exchange amount as the Φ9.52mm coppe tube heat exchange, the coppe mateial that can be saved is 41.8% and the aluminum foil mateial that can be saved is 50%. Keywods small diamete inne-gooved coppe tube; fin tube heat exchange; heat tansfe pefomance; cost analysis 0 Peface Coppe is one of the impotant aw mateials of the ai conditione. Even though coppe deposits in China ae anked 7th in the wold, the poduction sites ae elatively dispesed. The poduction amount is low and it is still vey fa off when compaed to the aveage intenational standad. 4/5 of the coppe aw mateial equied by domestic entepises evey yea is impoted. Coppe pices emain high and this situation bings immense pessue to the cost competition among vaious ai-conditioning entepises. Replacing coppe tubes with aluminum tubes and using coppe tubes with smalle tube diametes ae the two popula tends cuently among ai-conditioning entepises to lowe cost. Because using coppe tubes with smalle diamete does not equie elatively lage impovements in the aeas of facilities and technologies, this has become the pefeed cost-loweing choice fo ai-conditioning entepises cuently. This epot fist adopts the single tube pespective to descibe the heat exchange pefomance and gam pe mete advantages of the Φ5mm inne-gooved coppe tube vesus the Φ9.52mm inne-gooved coppe tube. Afte that, the heat exchange model is constucted. Pefomance and cost compaisons ae done specifically fo the heat exchanges using these two kinds of tube diametes. With this as a basis, the impovement methods that need to be adopted in the couse of eplacing the Φ9.52mm coppe tube heat exchange with the Φ5mm coppe tube heat exchange, as well as the cost advantage this eplacement bings, will be set out. 1 Pefomance and Cost

2 Compaisons of Two Kinds of Inne-Gooved Coppe Tubes The inne-gooved tube is a kind of high efficiency heat exchange component. Because it possesses 2~3 times the heat exchange capability of the nomal bae tube, it has eceived extensive attention. The high efficiency of the inne-gooved tube stimulates and pomotes the development of enegy saving, high efficiency and miniatuization fo ai-conditioning systems. The typical inne-gooved tube tooth-type paametes ae as shown in Figue 1. Of them, d is the oute diamete, δ is the tube wall thickness, h is the tooth height, β is the helix angle, γ is the tooth vetex angle and N is the tooth numbe. Table 1 shows the fequently used tooth-type paametes and gam pe mete fo the Φ9.52mm and Φ5mm inne-gooved coppe tubes. It can be seen that the Φ5mm inne-gooved tube when compaed to the Φ9.52mm inne-gooved tube has a substantial dop in the gam pe mete. Figue 1 Schematic Diagam of Inne-Gooved Tube Stuctue Table 1 Paametes fo Two Kinds of Inne-Gooved Coppe Tubes Bottom Tooth Oute Tooth Helix Tooth Gam Wall Vete Diamete Heigh Angl Numbe Pe Thicknes x t e Mete s Angle (mm) (mm) (mm) ( ) ( ) (g/m) By using the single tube phase change heat exchange test bench, we tested and soted out fo the Φ9.52mm and Φ5mm coppe tubes the changing situation of the local heat exchange coefficient within the tubes unde diffeent dyness conditions, as well as the changes of the aveage heat exchange coefficient within the tubes duing diffeent volume flow. The testing efigeants used wee all R22. The condensing tempeatues wee all 45 C. The inne-gooved tooth-type paametes used wee the same as those in Table 1. Figue 2 descibes the situation of the local heat exchange coefficient within the two kinds of inne-gooved coppe tubes changing accoding to the dyness of the efigeant. Fom the figue, it can be seen that: as the dyness of the efigeant inceases, the local heat exchange coefficient of the efigeant within the tube pesents a ising tend. Within the entie dyness change scope, compaed to the Φ9.52mm inne-gooved coppe tube, the local heat exchange coefficient within the Φ5mm inne-gooved coppe tube is highe by 10-15%. Figue 3 descibes the situation of the aveage heat exchange coefficient within the two kinds of inne-gooved coppe tubes changing accoding to the volume flow of the efigeant. Fom the figue, it can be seen that: as the volume flow of the efigeant inceases, the aveage heat exchange coefficient of the efigeant in the entie two-phase egion also pesents a ising tend. Within the entie flow change scope, compaed to the Φ9.52mm inne-gooved coppe tube, the aveage heat exchange coefficient within the Φ5mm inne-gooved coppe tube is coespondingly highe by 10-15% too.

3 Heat Exchange Coefficient h:w/m 2 K Heat Exchange Coefficient h: W/m 2 K d 2 dp ws u dz dz A Enegy consevation equation: (2) mm Inne-Gooved Tube 5mm Inne-Gooved Tube d dz uh D A q w (3) 3000 Figue 2 Local Heat Exchange Coefficients of Φ9.52 and Φ5 Coppe Tubes Duing Diffeent Dyness Figue 3 Aveage Heat Exchange Coefficients of Φ9.52 and Φ5 Coppe Tubes Duing Diffeent Volume Flow 2 Constucting and Checking Heat Exchange Model Dyness x Volume Flow G:kg/m 3s This section uses the finite volume method as basis to patition the nodes fo the fin tube heat exchange coe body model. A one-dimensional steady-state distibution paamete model [1] was constucted. The contol equations ae as below: Mass consevation equation: d u 0 dz Momentum consevation equation: 9.52 mm Coppe Tube 5mm Coppe Tube (1) Of the above, A, w, s q and w ae the tube passage coss-sectional aea, shea stess, suface heat exchange aea within the tube and heat flow espectively. The calculation coelation equation within the tube comes fom a efeence document [2]. The ai-side coelation equation comes fom anothe efeence document [3]. It must be made clea that: the heat exchange amount calculations fo this model use the effectiveness-numbe of tansfe units method. Because the efigeant needs to flow though the ove-hot zone, two-phase zone and ove-cold zone fom enty to exit, calculations must be done by handling it as two kinds of situations the single-phase zone and the two-phase zone. The ai side was unde a dy opeating condition fom the beginning and it is calculated as pe a single-phase model. The bae tube heat exchange calculation of this model is checked against the CoilDesigne softwae developed by the Univesity of Mayland. The inne-gooved tube heat exchange model is also compaed against the heat exchange laboatoy test esults. The heat exchange deviations ae all within 5%. This poves that the cuent model is definitely effective. 3 Pefomance and Cost Compaisons of s Below, the two kinds of Φ9.52mm and Φ5mm inne-gooved coppe tube heat exchanges ae used as examples to descibe the cost advantage a heat exchange with a small tube diamete has when the heat exchange pefomance of the two ae close.

4 In the calculations, the two types of Φ9.52mm inne-gooved coppe tube and Φ5mm inne-gooved coppe tube heat exchanges ae calculated using the same enty paametes as pe Table 2. See Table 3 fo the stuctual paametes of the Φ9.52mm inne-gooved coppe tube heat exchange. See Table 4 fo the stuctual paametes of the Φ5mm inne-gooved coppe tube heat exchange. The vaious manifold layouts ae as shown in Figue 4. The calculation esults show that afte adjusting the tube numbe and tube spacing (spacing in the T-diection and spacing in the N-diection), the Φ5mm inne-gooved coppe tube heat exchange can each almost the same heat exchange pefomance as that of the Φ9.52mm inne-gooved coppe tube heat exchange: fo the Φ9.52mm inne-gooved coppe tube heat exchange, the heat exchange amount is 3670W and the supecooling tempeatue is 10 C; fo the Φ5mm inne-gooved coppe tube heat exchange, the heat exchange amount is 3637W and the supecooling tempeatue is 7 C. Fom the pespective of cost analysis, the Φ9.52mm coppe tube heat exchange uses 12 coppe tubes and 6 U tubes. The total weight is 537.7g. The Φ5mm coppe tube heat exchange uses 18 coppe tubes and 9 U tubes. The total weight is 312.9g. The coppe tube usage amount is educed by 41.8%. The T-diection spacing of the heat exchanging tubes in the Φ5mm coppe tube heat exchange is half the T-diection spacing of the heat exchanging tubes in the Φ9.52mm coppe tube heat exchange. The length and height ae the same fo both kinds of heat exchanges. Theefoe, the aluminum foil usage amount fo the Φ5mm coppe tube heat exchange is educed by half. Table 2 Calculated Opeating Condition Paametes fo Paamete Value Unit Ai Inlet Dy-Bulb 35 Ai Inlet Wet-Bulb 24 Ai Inlet Ai Speed 1.5 m/s Atmospheic kpa Pessue Refigeant Type R22 - Flow kg/s 75 Pessue 2530 kpa Table 3 Stuctual Paametes fo Φ9.52mm Paamete Symbol Value Unit Length L 500 mm Height H 306 mm T-Diection S1 22 mm N-Diection S mm Fin Type Louveed Window - Fin Thickness δ f mm Fin Ft 1.2 mm Table 4 Stuctual Paametes fo Φ5mm Paamete Symbol Value Unit Length L 500 mm Height H 306 mm T-Diection S1 11 mm N-Diection S2 17 mm Fin Type Louveed -

5 Window Fin Thickness δ f mm Fin Ft 1.2 mm Figue 4 Flow Chat fo Φ9.52mm and Φ5mm exchange pefomance as the Φ9.52mm inne-gooved coppe tube heat exchange. The coppe tube usage amount can also be educed by 41.8%. The aluminum foil cost is educed by aound 50%. (3) While keeping the windwad coss-sectional dimensions unchanged, though adjusting the efigeant manifold and tube spacing, as well as stuctual paametes like the fin spacing, the heat exchange with small tube diamete can obtain the same pefomance as the coppe tube heat exchange with big tube diamete. Refeence Documents [1] Yang Shiming and Tao Wenquan. Heat Tansfe Studies. 4th edition. Beijing: Highe Education Pess, [2] M.K. Dobson, J.C. Chato, Condensation in Smooth Hoizontal Tubes, Tansactions of the ASME, Jounal of Heat Tansfe 120 (1998) [3] Wang Qichuan. Design. Taipei: Wunan Pess, 2005 Inne-Gooved Coppe Tube s 4 Conclusion Fo this epot, eseach was fist conducted fo the single tube pefomance and cost of the two kinds of Φ9.52mm and Φ5mm inne-gooved coppe tubes. Afte that, the steady-state distibution paamete model fo the tube fin heat exchange was constucted. Reseach was then caied out egading the pefomance and cost of the tube fin heat exchanges that use the two abovementioned kinds of diffeent diamete inne-gooved coppe tubes. The conclusion obtained is as below: (1) Unde the same testing conditions, the heat exchange coefficient within the Φ5mm inne-gooved coppe tube is aound 15% highe than that within the Φ9.52mm inne-gooved coppe tube. The mateial cost is thus geatly educed; (2) Fo the same dimensions and unde the same opeating conditions, the Φ5mm inne-gooved coppe tube heat exchange can achieve almost the same heat

Optimal Design of Smart Mobile Terminal Antennas for Wireless Communication and Computing Systems

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