Effect of multiple jet impingement plate configurations on Reynolds Number in a pipe

Transcription

1 IOP Conference Series: Materials Science and Engineering PAPER OPEN ACCESS Effect of ultiple jet ipingeent plate configurations on Reynolds Nuber in a pipe To cite this article: M S Rali et al 06 IOP Conf. Ser.: Mater. Sci. Eng View the article online for updates and enhanceents. This content was downloaded fro IP address on 0//07 at 0:6

2 IOP Conf. Series: Materials Science and Engineering 5 (06) 00 doi:0.088/ x/5//00 Effect of ultiple jet ipingeent plate configurations on Reynolds Nuber in a pipe M S Rali, A R Abu Talib, *, M Y Harin, and H R Mohd Saiah Departent of Aerospace Engineering, niversiti Putra Malaysia, Malaysia. Aerospace Manufacturing Research Centre, niversiti Putra Malaysia, Malaysia. * abdrahi@up.edu.y Abstract. Experiental investigations were carried out to study the effect of varying ultiple jet ipingeent plate configurations on Reynolds Nuber (Re) in a closed conduit. Air was considered as the working fluid. There were six ultiple ipingeent plates used for this experient where each plate has a different hole configurations that include the hole diaeter, hole orientation, pitch in x-direction and pitch in y-direction. Four sets of orifice plate with diaeter of 0.0, 0.03, 0.04, and 0.05 were used to get the ass flow rate in the pipe. Air was sucked through the ipingeent plate for five different settings of suction fan with an interval of 0Hz fro 0 to 50Hz. By taking the data for constant suction fan setting at 50Hz, it was found that the ipingeent hole orientation for both in-line and staggered does not give any effect on the Re obtained since the differences was considerably sall and fell within the accepted errors. Meanwhile, ipingeent hole diaeter was found to be directly proportional with the Re obtained. It was also found that the different pitch in ultiple hole ipingeent plate resulted in changes of Re. The results show that the Re was decreasing with higher pitch. The uncertainty analyses for the Re were also presented.. Introduction In the field of pipes flow easureent, Reynolds nuber (Re) is one of the iportant and critical paraeters to be deterined. The effect of Re as one of the iportant paraeters in jet ipingeent heat transfer field has been widely discussed and can be found in nuerous literatures and books. The effect of Re on the developent of flow structures in round jets has been explored by Diotakis [] who cae out with the proposed critical value of Re 0000, beyond which flow properties such as ixing becoe a weak dependence of Re. Kwon and Seo [] investigated the effect of Re on the behaviour of round jets using particle iage velocietry (PIV). Applying a range of low Re 77 54, they found out that the length of the zone of flow developent decreased with increasing Re centerline velocity decayed ore rapidly. Lee et al. [3] investigated the effects of jet-to-target plate distance and Re on the heat transfer fro an array of jets ipinging on a flat plate. They found out that the local and spatially averaged Nusselt nubers (Nu) showed strong dependence on the ipingeent jet Re for all situations exained. Goldstein et al. [4] investigated an injection of air perpendicular to the target surface. They dealt with high range of Re ( ). They concluded that even with high jet Re, the dependency of Nu over jet-to-target distance did not change. They also gave the correlation of heat transfer as Nu/Re 0.76 for all jet-to-target distance values. Meanwhile, Goldstein and Seol [5] concluded that the dependence of Nu on the jet Re could be approxiated by Nu/Re 0.7. Furtherore, Mohd Saiah [6] investigated single jet ipingeent heat transfer with Re ranging fro 0000 to It was found that the optial jet ipingeent Re Content fro this work ay be used under the ters of the Creative Coons Attribution 3.0 licence. Any further distribution of this work ust aintain attribution to the author(s) and the title of the work, journal citation and DOI. Published under licence by Ltd

3 IOP Conf. Series: Materials Science and Engineering 5 (06) 00 doi:0.088/ x/5//00 for 5 hole diaeter was at 0567 and any increase in Re would result in overdeveloped potential core, which lowered the heat transfer process [6]. The optial jet ipingeent Re for 0 hole diaeter was found to be at 8567 and lower Re would result in an underdeveloped potential core. All the aforeentioned literatures has proven that the effect of Re is very iportant to fluid flow experients. Inspired by the work of Mohd Saiah [6], which involved a single hole jet ipingeent heat transfer, this study will investigate the effect of ultiple hole ipingeent configurations on the pipe Re. There are three ain configurations for ipingeent plate, which are the hole diaeter, pitch and orientation. The effect of these three configurations will be investigated and exained.. Methodology Re for internal flow in a circular pipe can be expressed as: VD Re () ν where V ean velocity in /s, D characteristic length of the geoetry (diaeter in this case) in andν µ/ρ kineatic viscosity of the fluid in /s. There are three types of flow for Re, which are lainar, transition and turbulent flow. According to Yunus and Robert [7], the flow in a circular pipe is lainar for Re < 300, turbulent for Re > 4000, and transitional in between. Re < 300 lainar flow 300 Re 4000 transitional flow Re > 4000 turbulent flow The design of the experiental rig was based on Son et al. [8] and Mohd Saiah [6]. Although the objective of this study is not siilar with the aforeentioned researchers, design of their experiental set-up can still be used since it can deterine the flow characteristics such as fluid ass flow rate, fluid velocity and Re. The British standard BS04 [9] was chosen as a reference docuent since it provides the detailed geoetry paraeters for fabrication, instalent reuireents and working conditions for priary devices. The conduit used in this study is a straight cylindrical passage of constant cross-sectional area and has a length that ensures the upstrea fluid flow approaching the orifice plate is fully developed profile and free of swirl. This length is also known as hydrodynaic entry length, L h that is coonly taken to be the distance fro the pipe inlet to the point at which the velocity boundary layer erges at the centreline as shown in Figure [7]. L h Figure. The developent of the velocity boundary layer in a pipe [7] The hydrodynaic entry length is different for both lainar and turbulent flow. According to Kays and Crawford [0], Shah and Bhatti [] and also Zhi-ing [], the approxiate length of L h for lainar and turbulent flow can be approxiated as 5D and 0D, respectively. However, the pipes

4 IOP Conf. Series: Materials Science and Engineering 5 (06) 00 doi:0.088/ x/5//00 used in practice are coonly several ties the length of the entrance region, so that the flow through the pipes is fully developed. In this study, the recoended length for upstrea and downstrea sections based on BS04 were 0D and 6D, respectively [9], where the D for the pipe was eual to 0.. Figure shows a scheatic diagra of the experiental rig set-up. Orifice Plate 6D 0D D Suction Fan Pressure Tapings Intake Ipingeent Figure. Scheatic diagra of the experiental rig set-up.. Intake nozzle In this study, the chosen type for intake nozzle was ISA93. The intake nozzle, as the nae iplies, directs the fluid into the test rig in an appropriate anner. The intake nozzle was situated at the ost front section of the test rig. The earlier section of the test rig was a rectangular shape conduit, hence the cross-sectional diaeter of the conduit at this section will be replaced by the hydraulic diaeter, D H that Holan [3] defined as: D D H H 4 A P 4( ab) a + b where in Euation (), A is the cross-sectional area of the conduit and P is the wetted perieter of the conduit. Euation () can also be rearranged to Euation (3), in which a and b are both the sides of a rectangular. The inner cross-sectional area for the intake nozzle was 00 x Ipingeent plates There are six ultiple holes ipingeent plates that were used in this study. Each ipingeent plate had a different configuration in ters of hole diaeter, hole orientation as well as pitch in x- and y- direction as listed in Table. Figure 3a and Figure 3b illustrate the overview of the ipingeent plate. Note that the pitch in x- and y-direction is the center-to-center spacing of holes..3. Orifice plates Orifice plate can be defined in various ways [9, 4]. The ain iportant characteristic of this priary device is that it provides an abrupt change in the cross-sectional area of the conduit and thus results in a change of energy. Orifice plate had becoe the ost preferable flow eter due to its versatility, cost effectiveness and siple construction. () (3) 3

5 IOP Conf. Series: Materials Science and Engineering 5 (06) 00 doi:0.088/ x/5//00 Table. Six ultiple holes ipingeent plates with different configurations Ipingeent Plates Hole Diaeter () Hole orientation Pitch x- direction () Pitch y- direction () Nuber of holes A 7.0 in-line B 7.0 Staggered C 5.0 in-line D 5.0 staggered E 5.0 in-line F 5.0 staggered Pitch x-direction Hole 00 Pitch y-direction 00 (a) Pitch x-direction Hole 00 Pitch y-direction 00 (b) Figure 3. (a) Multiple holes ipingeent plate with in-line orientation, (b) Multiple holes ipingeent plate with staggered orientation 4

6 IOP Conf. Series: Materials Science and Engineering 5 (06) 00 doi:0.088/ x/5//00 There is a total of four orifice plates used in this study, which each of the has a diaeter of 0.0, 0.03, 0.04 and 0.05, respectively. Pressure easureents on orifice plate can be divided into three different approaches [9]. For this study, one approach was selected due to its siplicity, which was the D / and D pressure taps, where D is the pipe s inner diaeter and D is the orifice diaeter as shown in Figure 4. l D / l D Downstrea Section D D pstrea Section Figure 4. Orifice plate pressure tapings The principle of an orifice plate is based on the easureent of static pressure difference between the upstrea and downstrea sides. Based on ISO567 [5] and ASME MFC-3M [6], the ass flow rate, in pipe by using an orifice plate can be deterined with the following euation: where C is the discharge coefficient, A is the orifice area, ρ is the density at upstrea side and is the diaeter ratio between pipe and orifice which is D /D. Here the differential pressure, p can be easured by eans of a digital anoeter HHP 0. Note that C is dependant of the diaeter ratio, and the pipe's Re. Euation (5) shows the governing relationship for discharge coefficient, C [9]. in which L is a ratio of l /D, L is a ratio of l /D with l is the distance of the downstrea pressure tap fro the downstrea face of the orifice plate. Whenever L ter ( ) L C CA. p. ρ ( ) L' (4) (5), will be used for the. In this study, L euals to, therefore the orifice discharge coefficient yields: C L Orifice Plate L' The calculation of C is an iterative process since Re is needed to calculate C, but the velocity in the pipe needed for Re cannot be deterined until C is known. However, this iterative process converges uite rapidly in just one or two iterations. / Re 6 0 Re (6) 5

7 .4. ncertainty analysis Predictions of errors are vital for researchers, especially for those who are dealing with experiental works. Experientation is not just about taking the data. Each instruent has its own accuracy, hence the prediction of uncertainties is doinated by the accuracy errors that are also known as the rando errors. The uncertainty analysis will provide the inforation for experienters in knowing the scatter and how far the experiental data ay deviate fro the true value. For this study, uncertainty analyses for Re obtained have been done by using Taylor Series Method (TSM) for propagation of uncertainties. Euation (7) is given by Hugh and Glenn [7] that describes the propagation of overall uncertainties in easured variables into the overall uncertainty of the result. (7) where r is the function of two or ore variables and i is the uncertainty for variable X i. Referring to Euation (8) for Re, there are only two variables that have been considered as sources of error, which are air velocity, V and pipe diaeter, D while air density, ρ and air viscosity, µ are assued to be constant. (8) The air velocity, V can be defined fro the ass flow rate, as shown in Euation (9). (9) To get the uncertainty for V, the uncertainty for needs to be deterined first. Fro the Euation (4), by using the general uncertainty analysis in Euation (7), the uncertainty for is deterined as: (0) By taking the derivatives of with respect to the variables, then substituting it into Euation (0) and dividing by yields: () Then, by applying the Euation (7) again to the Euation (9), the uncertainty for V was deterined as: () Thus, the uncertainty for Re was deterined as: (3) / J i i i X r r µ ρ.. Re D V.A V ρ p p A A + + ( ) ( ) + + p p A A ( ) ( ) + A A V V Re Re + D D V V AEROTECH VI - Innovation in Aerospace Engineering and Technology IOP Conf. Series: Materials Science and Engineering 5 (06) 00 doi:0.088/ x/5//00 6

8 IOP Conf. Series: Materials Science and Engineering 5 (06) 00 doi:0.088/ x/5//00 Table shows the accuracy of the easuring devices that have been used in this study. Table. Measuring devices used with their accuracy Measuring Devices Accuracy Digital Manoeter HHP 0 0.% reading +0. % full scale + digit (full scale of 3 kpa) Digital Caliper ± 0.00" / 0.0 Ruler ± 0.05 c 3. Results and discussions Table 3 shows the results of Re with their uncertainties for each setting of orifice diaeter and suction fan without ipingeent plate being attached. Meanwhile, Table 4 to Table 9 show the results of Re with their uncertainties for each orifice diaeter and suction fan setting for every ipingeent plate. Since pressure gives the ost contribution to uncertainties values, the uncertainties percentage values obtained for Re were considerably high at saller pressure difference, which was up to ±5%. This was due to the fact that the range of the digital anoeter used was uite high for this experient and it only has better accuracy for larger pressure difference easureents. For that reason, only Re with uncertainties below 30% were selected and Re with uncertainties ore than 30% were neglected. Table 3. Reynolds nuber with uncertainties for each orifice diaeter and suction fan setting without ipingeent plate Orifice Diaeter () Suction Fan Setting (Hz) Reynolds Nuber, Re 0 98 ± % 760 ± 5.06 % null null 0 70 ± 6.55 % 390 ± 3. % 460 ± 38.4 % 4350 ± 5.06 % ± 7.4 % 5070 ± 9.76 % 700 ± 6.55 % 8540 ± 8.84 % ± 4.44 % 6840 ± 5.5 % 9870 ± 8.4 % 00 ± 6.55 % ± 3.5 % 8500 ± 3.76 % 00 ± 5.74 % 4000 ± 0.6 % Table 4. Reynolds nuber with uncertainties for each orifice diaeter and suction fan setting for ipingeent plate A Orifice Diaeter () Suction Fan Setting (Hz) Reynolds Nuber, Re 0 65 ± 5.06 % null null null ± 3. % 550 ± 38.4 % 700 ± 5.06 % null ± 9.03 % 3880 ± 6.55 % 460 ± 38.4% 4350 ± 5.06 % ± 5.9 % 570 ± 9.03 % 6500 ± 9.8% 740 ± 38.4 % ± 3.69 % 6530 ± 6.0 % 7940 ±.9 % 8540 ± 8.84% 7

9 IOP Conf. Series: Materials Science and Engineering 5 (06) 00 doi:0.088/ x/5//00 Table 5. Reynolds nuber with uncertainties for each orifice diaeter and suction fan setting for ipingeent plate B Orifice Diaeter () Suction Fan Setting (Hz) Reynolds Nuber, Re 0 65 ± 5.06 % 760 ± 5.06 % null null ± 9.8 % 550 ± 38.4 % 700 ± 5.06 % null ± 8.4 % 450 ± 4.5 % 530 ± 8.84 % 4350 ± 5.06 % ± 4.9 % 5470 ± 8.4 % 700 ± 6.55% 740 ± 38.4 % ± 3.46 % 6840 ± 5.5 % 8760 ± 0.6 % 9530 ± 3.0 % Table 6. Reynolds nuber with uncertainties for each orifice diaeter and suction fan setting for ipingeent plate C Suction Fan Setting (Hz) Orifice Diaeter () Reynolds Nuber, Re 0 65 ± 5.06 % 760 ± 5.06% null null ± 3.0 % 550 ± 38.4 % 700 ± 5.06 % null ± 9.03 % 3600 ± 9.8 % 460 ± 38.4 % 4350 ± 5.06 % ± 5.5 % 4850 ± 0.6 % 5940 ± 3.0% 6090 ± 57.57% ± 3.78 % 600 ± 6.6 % 7490 ± 4.5 % 740 ± 38.4 % Table 7. Reynolds nuber with uncertainties for each orifice diaeter and suction fan setting for ipingeent plate D Suction Fan Setting (Hz) Orifice Diaeter () Reynolds Nuber, Re 0 65 ± 5.06 % null null null ± 3. % 090 ± % 700 ± 5.06 % null ± 9.76 % 3600 ± 9.8 % 3790 ± % 4350 ±.53 % ± 5.5 % 4850 ± 0.6 % 530 ± 8.84 % 6090 ± % ± 3.78 % 600 ± 6.99 % 700 ± 6.55 % 740 ± 38.4 % Table 8. Reynolds nuber with uncertainties for each orifice diaeter and suction fan setting for ipingeent plate E Suction Fan Setting (Hz) Orifice Diaeter () Reynolds Nuber, Re 0 65 ± 5.06 % null null null 0 90 ± 8.84 % 490 ± 5.06 % null null ±.6 % 940 ± 8.84 % 700 ± 5.06 % null ± 6.63 % 3880 ± 6.55 % 3790 ± % 4350 ± 5.06 % ± 4.44 % 4630 ±.66 % 530 ± 8.84 % 4350 ± 5.06 % 8

10 IOP Conf. Series: Materials Science and Engineering 5 (06) 00 doi:0.088/ x/5//00 Table 9. Reynolds nuber with uncertainties for each orifice diaeter and suction fan setting for ipingeent plate F Suction Fan Setting (Hz) Orifice Diaeter () Reynolds Nuber, Re 0 65 ± 5.06 % null null null 0 90 ± 8.84 % 090 ± % 700 ± 5.06 % null ± 0.6 % 940 ± 8.84 % 3790 ± % 4350 ± 5.06 % ± 6.3 % 450 ± 4.5 % 460 ± 38.4 % 4350 ± 5.06 % ± 4.9 % 5070 ± 9.76 % 5940 ± 3.0 % 6090 ± % Figure 5 shows the Re at 50 Hz without ipingeent plate being attached. These values of Re can be used as a benchark to other Re values obtained with ipingeent plates. Figure 5. Re without ipingeent plate being attached 3.. Effect of ipingeent plate hole orientations Figure 6 (a), (b) and (c) show the coparison of Re values for ipingeent plates that have a siilar hole diaeter and pitch but different holes orientation. All three graphs obviously give a uite siilar trend. At suction fan of 50 Hz, the Re for ipingeent plate A and B, C and D, and E and F increased siilarly with an increase of orifice diaeter regardless of the hole orientation. Though there were soe slight differences between Re values at orifice diaeter 0.04, they were considerably sall (not ore than 0%) and fell within the uncertainties. The sall differences were due to higher holes nuber in the ipingeent plate B, which resulted in higher open area and fluid ass flow rate. 3.. Effect of ipingeent plate hole pitch Figure 7 (a) and (b) show the coparison of Re values for ipingeent plates that have siilar hole diaeter and orientation but different pitch. All two graphs obviously give a uite siilar trend. At suction fan of 50 Hz, Re for ipingeent plate C and E, and D and F increased in different increents with an increase of orifice diaeter. This shows that different pitch on the ipingeent plates resulted in different Re. This was due to the fact that by having higher hole pitch, it will reduce the nuber of hole in the fixed area of ipingeent plate. This will result in a lower open area in the ipingeent plate and thus the fluid ass flow rate through the ipingeent plate will be reduced. 9

11 IOP Conf. Series: Materials Science and Engineering 5 (06) 00 doi:0.088/ x/5//00 Figure 6. (a) Coparison of Re between in-line and staggered ipingeent plates A and B for 7 hole diaeter Figure 6. (b) Coparison of Re between in-line and staggered ipingeent plates C and D for 5 hole diaeter with 5 pitch-x and 0 pitch-y 0

12 IOP Conf. Series: Materials Science and Engineering 5 (06) 00 doi:0.088/ x/5//00 Figure 6. (c) Coparison of Re between in-line and staggered ipingeent plates E and F for 5 hole diaeter with 0 pitch-x and 5 pitch-y Figure 7. (a) Coparison of Re between 5 pitch-x, 0 pitch-y and 0 pitch-x, 5 pitch-y ipingeent plates C and E for in-line orientation

13 IOP Conf. Series: Materials Science and Engineering 5 (06) 00 doi:0.088/ x/5//00 Figure 7. (b) Coparison of Re between 5 pitch-x, 0 pitch-y and 0 pitch-x, 5 pitch-y ipingeent plates D and F for staggered orientation 3.3. Effect of ipingeent plate hole diaeter Figure 8 (a) and (b) show the coparison of Re values for ipingeent plates that have siilar hole pitch and orientation but different diaeter. Though the hole pitch between ipingeent plate A and E, and B and F were not exactly the sae, their differences were sall and would not give significant effect to the overall Re since the nubers of hole were the sae. Thus the effect of hole diaeter can be investigated by using these ipingeent plates. All two graphs obviously show a rather siilar trend. At suction fan of 50Hz, Re for ipingeent plate A and E, and B and F increased in different increents with increase of orifice diaeter. This shows different hole diaeter on the ipingeent plates resulted in different Re. This was due to the fact that by having larger hole diaeter will result in a higher open area of the ipingeent plate and thus higher fluid ass flow rate through the hole. Conseuently, higher Re will be obtained. 4. Conclusion The overall goal of this experiental study was to exaine the effect of having different configuration of ultiple ipingeent plate on Re in a pipe. The configurations include the holes diaeter, hole pitch as well as hole orientation that were in-line and staggered. Based on obtained data for constant suction fan setting at 50Hz and for orifice diaeters of 0.0, 0.03 and 0.04, it was found that for the fixed area of ipingeent plates, orientation of the ipingeent plate does not give different Re as long as the nuber of ipingeent hole reains the sae. Meanwhile, Re was found to be lower when the holes pitch is higher. It shows that for fixed area of ipingeent plate, the holes pitch was inversely proportional with the Re. Also found in this study was that the ipingeent hole diaeter gives a significant effect on Re in a pipe. There was a directly proportional relationship between holes diaeter with Re obtained. The larger the holes diaeter, the higher the Re would be.

14 IOP Conf. Series: Materials Science and Engineering 5 (06) 00 doi:0.088/ x/5//00 Figure 8. (a) Coparison of Re between hole diaeter of 7 and 5 ipingeent plates A and E for in-line orientation Figure 8. (b) Coparison of Re between hole diaeter of 7 and 5 ipingeent plates B and F for staggered orientation 3

15 IOP Conf. Series: Materials Science and Engineering 5 (06) 00 doi:0.088/ x/5//00 Acknowledgeent The first author likes to thank the Ministry of Higher Education Malaysia for provision of MyBrain5 scholarship. References [] Diotakis P E 000 J. Fluid Mech 409 pp [] Kwon S J, Seo I W 005 Exp. Fluids 38 pp [3] Lee J, Ren Z, Ligrani P, Fox M D and Moon H 05 International Journal of Theral Sciences 88 pp. 7-8 [4] Goldstein R J, Behbahani A I and Heppelann K K 986 International Journal of Heat Transfer 9 pp [5] Goldstein R J and Seol W S 99 International journal of Heat and Mass Transfer 34 pp [6] Mohd Saiah H R 0 Effects of Non-Isotheral Single Circular Ipinging Jet on a Quasi- Adiabatic Flat Plate Master of Science Thesis niversiti Putra Malaysia, Malaysia [7] Yunus A C and Turner R H 005 Fundaentals of Theral-Fluid Sciences (New York: McGraw-Hill) [8] Son C, Gillespie D, Ireland P and Dailey G M 00 Journal of Turboachinery 3 pp [9] BS04 British Standard 98 Measureent of fluid flow in closed conduit [0] Kays W M and Crawford M E 993 Convective Heat and Mass Transfer (New York: Mc- Graw Hill) [] Bhatti M S and Shah R K 987 Handbook of Single-Phase Convective Heat Transfer (New York: Wiley Interscience) [] Zhiing W 98 Applied Matheatical Mechanic 3 p. 433 [3] Holan J P 997 Heat Transfer (New York: McGraw-Hill) [4] Daniel 997 Measureent and control, fundaentals of orifice eter easureent Daniel Docuents/Fundaentals-of- Orifice-Measureent-techWpaper.pdf [5] ISO Measureent of fluid flow by eans of pressure differential devices inserted in circular cross-section conduits running full part : Orifice plate [6] ASME MFC-3M 004 Measureent of fluid flow in pipes using orifice, nozzle, and venturi [7] Colean H W and Steele W G 009 Experientation, Validation, and ncertainty Analysis for Engineers (New Jersey: John Wiley & Sons) 4