Heat exchange tube

FIELD: heating.

SUBSTANCE: in a heat exchange tube, the channel of which has projections and grooves, according to the proposed invention, the channel is formed with plain tube sections and narrow grooves with geometrical ratios: h/D=0.1, (t-l)/h=1, l/h<(3-5) where h - projection height, mm, D - inner diameter of the heat exchange tube, mm, t - length of a typical section of the channel with a projection and a groove, mm, l - groove length, mm.

EFFECT: use of the proposed heat exchange tube will allow reducing consumption of energy for pumping of heat carriers through a heat exchange unit by 2,5-4 times in comparison to a plain-tube heat exchange unit owing to reducing hydraulic resistance.

4 dwg, 1 tbl

 

The present invention relates to the field of energy and can be used in transport, chemical engineering and other branches of engineering.

Known heat pipe [Nazmeen YG, Konahin A.M., Idols B.A., Alimpiev CENTURIES Experimental study of heat transfer in laminar flow in tubes using wire spiral inserts. // Abstr. jubilee scientific conference. Kazan branch of Moscow. the saving. in-TA. Kazan: KF MEI, 1993. P.12-14], the channel which is made from coiled wire insert ("channel 1"). Channel "1" as an intensifier heat transfer (it) serves as a wire insert. Optimal for this channel are the parameters h/D=0,171; t/D=4,3, where h is the height of the protrusion, D - internal pipe diameter, t - step ledges. The experiments were conducted in a limited range of characteristic parameters h/D=0,0714-0,171; t/D=0,714-4,3; Re=400-1000, where Re is the Reynolds number.

The closest analogue to the claimed invention is a heat pipe [Nazmeen YG, Konahin A.M., Idols B.A., Alimpiev VV Heat transfer and hydraulic resistance in laminar flow of viscous fluid in the pipes with artificial roughness. // Thermal engineering. 1993. No. 4. P.66-69], the channel which is made with protrusions and grooves (channel 2"). In the channel "2" as an intensifier heat transfer (it) are narrow annular made the s on the inner surface of the pipe (l< t, where l is the length of the groove, t is the length of a typical section of the channel lip and groove). For channel "2" model was used [Alimpiev CENTURY Model for calculation of heat transfer and resistance of channel ledges at Re<104.// WPI. higher education institutions. Aviation equipment. 2001. No. 2. P.48-52], a summary of which follows. In the stream after a low ledge (h/D<0,1, where h is the height of the protrusion, D - inner diameter of the tubes is formed with a recirculation zone (RZ) RZ1. From the edge of the ledge on the surface of RZ1 and forth along the wall develops internal wall boundary layer (UPU) ITS thickness δ. Under RZ1 occurs VPS. At low protrusion corresponding to the rational conditions of heat exchange intensification (ITO), rapid relaxation currents in ITS and ITS to "standard" laminar boundary layer (LPS), characteristic of the plate (Blasius). Therefore, the calculation of α (heat transfer coefficient) and τ (shear stress friction) in ITS and ITS possible theory for plates. The section of the channel (and flow) of length t - model (recurring), therefore, the averaged values of α and τ for the segment t and the same channel. Thermal and dynamic (taking into account the resistance of the ledge) interaction of the flow with a wall at the site t is fully determined by transport processes in ITS and ITS. In the stream above the laminar-turbulent the aqueous transition (TLP) intensification of heat transfer (ITO) explains basically, low resistance thin VPS and VPS. The experiments were conducted only for the outer surface of the pipe in the annular flow heat exchanger (TA), in a limited range of characteristic parameters - t/D<3.5; Re=400-1200, where Re is the Reynolds number.

The disadvantages of the known heat exchange tubes are high flow rates and low efficiency.

The task, which is aimed by the invention is the improvement of energy efficiency by reducing flow rates.

The technical result is achieved that the heat exchange tube to which the channel is made with the protrusions and grooves, according to the claimed invention, a channel is formed smooth the pipe sections and narrow grooves with geometric proportions:

h/D=0.1, (t-l)/h=1, l/h<(3-5),

where h is the height of the ledge, mm,

D - internal diameter of the tubes, mm,

t - the length of a typical section of the channel lip and groove, mm,

l is the length of the groove, mm

The invention is illustrated by drawings and table 1 shows the channel proposed heat pipe (channel "3"), 2, 3, 4, table 1 shows the results of calculations of efficiency (heat exchange rate, the coefficient of hydraulic resistance, relative power ratio) of channels "1", "2" and "3".

Thus the om, to achieve the technical result of the proposed inventive design of the heat exchange tubes to which the channel (channel "3") formed a smooth pipe (t-l)>h and narrow grooves l/h<(3-5), i.e. the channel proposed heat pipe is a discrete-rough channel (DShK).

Flow pattern (and settlement) in the channel "3", figure 1, is based on the model [gortikov Û.F., Alimpiev CENTURIES, Abdrakhmanov, A.R., the Calculation of turbulent heat transfer and resistance in channels with transverse annular grooves. "Izv. higher education institutions. Aviation equipment. 1997. No. 3. P.56-63] for turbulent flow. Thermal-hydraulic calculation channel "3" is reduced to the calculation of α; τ on a typical plot of t and in laminar ITS and ITS.

Calculations of channels carried out under conditions identical with [gortikov Û.F., Alimpiev V.V., Popov IA the Efficiency of an industrial perspective intensification heat transfer. "Izv. Russian Academy of Sciences. Energy. 2002. No. 3. Pp. 102-118.; Leont'ev A.I., gortikov Û.F., Alimpiev V.V., Popov, I.A. Effective intensification of the heat transfer laminar (turbulent) flows in the channels of power.// WPI. Russian Academy of Sciences. Energy. 2005. No. 1. P.75-91]. The area calculations corresponds nominally laminar regime in a sleek channel - Re≥50. The coolant is air. The size of the intensifier heat transfer(AndT)-h =h/D=0,1=const. Performed multivariate calculations with different combinations of geometrical parameters of it for each channel.

The criterion of efficiency of the channel and the optimal size of it, as in the works [gortikov Û.F., Alimpiev V.V., Popov IA the Efficiency of an industrial perspective intensification heat transfer. "Izv. Russian Academy of Sciences. Energy. 2002. No. 3. Pp. 102-118; Leont'ev A.I., gortikov Û.F., Alimpiev V.V., Popov, I.A. Effective intensification of the heat transfer laminar (turbulent) potokov in the channels of power. "Izv. Russian Academy of Sciences. Energy. 2005. No. 1. P.75-91], served as the relative energy ratioE'=E'/Egl'=(Nu/Nugl)/(ξ/ξgl)=Nu/ξ(Nu is the number of Asselta, ξ - coefficient, CH - index smooth channel; no index - discrete-roughened channel (DShK). When comparing variants of the same channel (for each xed Re) the highest efficiency of the channel and the optimal size of it was a case ofE'=max.

To preserve the substance of the hydrodynamic picture wrap it in the calculations of the channels was observed obvious necessary conditions: for channel "2" - (t-l)>L, where L is the length of RZ1.

Some results of calculations of thermal-hydraulic channels "1", "2" and "3" on the basis of models and experimental data is shown in figure 2-4 and in table 1. Results are given for the most effective options for each channel. The optimal size of it is shown in table 1. The proposed heat exchanger pipe (channel "3") has the highest heat transfer, reachingNu=4at Re=1200, which is probably due to the peak of the heat transfer on the top of the narrow ledge (t-l)/h=1 (the initial part of the plate, figure 2, table 1. Heat dissipation channel "2" minimum. The proposed heat exchanger pipe (channel 3) has a better marker resistance, which is is lowest ( ξ=1,5at Re=1200) compared to other heat exchange tubes (channels "1", "2"). The increase in the resistance of the channel "3" (because of the presence of it) lags behind the increase in the heat transferNu>ξ(figure 2; figure 3, table 1), which provides high efficiency channel "3",E'=4at Re=400, figure 4, table 1.

Channels "1", "2", high resistance and low heat dissipation, greatly inferior to channel "3" on the efficiency. In most parts of the range Re, figure 4, channel "2" is less efficient than a smooth pipe.

Thus, in analysing the efficiency of heat exchange tubes with channels"1"; "2"; "3" found a previously unknown optimal geometrical relations of the proposed heat exchanger pipe (channel 3), which ensures fold reduction in weight and size characteristics of the heat exchanger (TA).

Need to discuss the actual flow regime in the channels"1"; "2"; "3" in the investigated interval of numbers Re=400-1200, presecenik the size of it. In the review [Alimpiev CENTURIES orcs in the channels of the heat exchangers with ledges-intensification of heat transfer. // Thermal engineering. 2001. No. 7. P.52-56] it is shown that the region of laminar-turbulent transition (LTP) in DShK can cover the range Re=200-4000. Extensive experiments on visualization of the flow of smoke and PIV-method for protrusion height ofh=0,15found that the beginning of the LTP complies with Re=1300 [Dushin O.A. Separation of the flow behind the tabs in the channel at low Reynolds numbers. // Abstract. Diss. Kida. technology. Sciences. Kazan: KSC RAS, 2012. 16 C.]. Therefore, it is reasonable to assume studied interval of Re number and size it is in the area of laminar flow DShK.

Efficiency and optimal sizes of channels

Table 1
Channel 1 (h/D=0,171, t/D=4,3)
Re4007001000
Nu/NuCH2,633,233,68
ξ/ξ CH2,483,52to 4.41
(E'/Egl')1,070,9160,83
Channel 2 (l1=100h; l2/D=3,5)
Re40080010001200
Nu/NuCH1,5011,626kzt1.6641,694
ξ/ξCH1,2861,9852,28of 2.514
(E'/Egl') 1,1680,8190,730,674
Channel 3 ((t-l)/h=1)
Re40080010001200
Nu/NuCH3,343,75a 3.9as 4.02
ξ/ξCH0,841,21,331,46
(E'/Egl')3,973,152,93was 2.76

The use of the proposed heat exchanger tubes will allow 2.5-4 times to reduce the energy consumption for pumping the coolant through the heat exchanger (TA), compared with gladmat ubnem heat exchanger, by reducing flow rates.

Therefore, opens the possibility of implementing high-performance variant of the heat exchanger (TA) and significant energy saving and construction materials.

The heat exchange tube to which the channel is made with the ridges and grooves, wherein the channel is formed of a smooth pipe and narrow grooves with geometric ratios:
h/D=0,1, (t-l)/h=1, l/h<(3-5),
where h is the height of the ledge, mm,
D - internal diameter of the tubes, mm,
t - the length of a typical section of the channel lip and groove, mm,
l is the length of the groove, mm.



 

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