CN200965443Y - A non-depositional scale plate type heat exchanger - Google Patents
A non-depositional scale plate type heat exchanger Download PDFInfo
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- CN200965443Y CN200965443Y CN 200620091827 CN200620091827U CN200965443Y CN 200965443 Y CN200965443 Y CN 200965443Y CN 200620091827 CN200620091827 CN 200620091827 CN 200620091827 U CN200620091827 U CN 200620091827U CN 200965443 Y CN200965443 Y CN 200965443Y
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Abstract
The utility model relates to an improved technology of heat exchanger, in particular to a non-scale deposition plate type heat exchanger. A cold fluid flow inlet at the upper part of an fixed press plate is connected with a cold fluid flow reflux general pipeline through an pipeline at the side of the fixed press plate of the normal plate type heat exchanger; a cold fluid flow outlet at the lower part of the fixed press plate is connected with a cold fluid flow outflow general pipeline through the pipeline. The utility model demonstrates the heat exchanger theory of heat transfer, which relates to that, the calculation formula of parallel-flow heat exchanging logarithm mean temperature difference is not applicable to the plate type heat exchanger, furthermore, the utility model also gives the calculation method of parallel-flow heat exchanging logarithm mean temperature difference. The utility model makes use of parallel-flow heat exchanging method, thereby making the cold and hot fluid flows flow in the plate type heat exchanger from upper to bottom, so as to realize the zero emission and on-line automatic pollution discharge of the plate type heat exchanger by using the impact function of the downward flow of the fluid flows and the gravity function of the scale particles, so as to achieve the purposes of preventing the scale deposition and dirt in the heat exchanging boards, thus enhancing the heat exchanging efficiency and saving the resources, which can be applied in heat supply and heating system and other departments.
Description
Affiliated technical field
The utility model relates to the improvement technology of heat exchanger, is specially a kind of plate type heat exchanger that does not have sediment incrustation.
Technical background
Plate type heat exchanger is made of one group of parallel thin plate stack, between adjacent panels, separate in twos and form passage with special gasket seal, flow in passage separately in the cold and hot fluid compartment of terrain, the plate type heat exchanger heat transfer coefficient is bigger, flow resistance is less, is widely used in departments such as heat supply heating system and food, medicine, chemical industry.According to the relative flow direction difference of cold and hot fluid in the heat exchanger, can be divided into downflow type, reverse-flow, cross flow, mixed-flow etc., downflow type, i.e. two kinds of parallel and co-flow of fluid; Reverse-flow, i.e. parallel the and reverse flow of two kinds of fluids; Cross flow, promptly two kinds of fluids are in orthogonal direction cross flow one; Mixed-flow, i.e. the combination of various flows flowing mode is flowed.
The heat exchanger theory of thermal conduction study is pointed out: " cold and hot fluid is under import and outlet temperature same case, and reverse-flow logarithmic mean temperature difference (LMTD) is greater than downflow type ", referring to: [U.S.] FP is because of pula, Crow, DP De Wit work, Yu Guangjing etc. translate, it is basic to conduct heat, Beijing: Yuhang Publishing House, 1987." under the conditions permit prerequisite, heat exchanger adopts counter-flow arrangement as far as possible ", referring to: scape morning sunlight chief editor, the thermal technology is theoretical and use Beijing: China Electric Power Publishing House, 2004.
Therefore, existing common plate type heat exchanger is all gone up and is done under the countercurrent flow situation, Fig. 2 is traditional plate type heat exchanger pipeline connection diagram, cold fluid is that the cold fluid import 21 from heat exchanger fixed pressure plate bottom enters heat exchanger, in heat exchanger, flow from bottom to top, export 23 outflow heat exchangers from fixed pressure plate top cold fluid again; Hot fluid enters heat exchanger from heat exchanger fixed pressure plate top hot fluid import 22, in heat exchanger, flow from top to down, export 24 outflow heat exchangers from fixed pressure plate bottom hot fluid again, sewage draining valve 10 is established in cold fluid outlet 23 on fixed pressure plate top, establishes sewage draining valve 10 in the hot fluid outlet 24 of fixed pressure plate bottom.Carry out heat exchange at fluid, in the cooling fluid temperature elevation process, on heat exchanger plates, generate the hard scale of chemisorbed, in fluid, separate out simultaneously a large amount of incrustation scale particulates, under the effect of Robert Van de Walle power, between the particulate, between original suspended particulate, adsorb mutually in particulate and the cold fluid, particle diameter constantly increases, bigger particle in the cold fluid, under the self gravitation effect, constantly be deposited in the heat exchanger, make heat exchanger become " contamination device ", between heat exchanger plates, form the sediment incrustation layer, have a strong impact on the heat exchange effect.Calculating the situation that scale crust thickness causes the heat exchange loss according to the heat transfer formula lists in the table one.
Table one cold fluid (water) deposits the heat exchange loss comparison sheet that the different-thickness scale crust causes between heat exchanger plates
| Scale crust thickness δ 2(mm) | 0.5 | 1.0 | 1.5 | 2.0 | Remarks |
| Coefficient K [W/ (m 2·℃)] | 943.1 | 715.8 | 579.0 | 485.4 | Adverse current; Cold water is through the online processing in electromagnetic field of high frequency |
| Coefficient K ' [W/ (m 2·℃)] | 1169.2 | Following current: cold water is through the online processing in electromagnetic field of high frequency | |||
| Heat exchange loss late η (%) | 19.3 | 38.8 | 50.5 | 58.5 | η≡(K′-K)/K′ |
Data are following calculating in the table, when cold and hot fluid (water-water) in plate type heat exchanger during countercurrent flow, its coefficient of heat transfer K is provided by following formula
K＝{1/h
1+δ
1/λ
1+δ
2/λ
2+1/h
2}
-1 (1)
H in the formula
1-hot water side the coefficient of heat transfer (2000～7000) [W/ (m
2℃)], get 3000; Referring to: Li Shanhua etc. write, practical central heating handbook, Beijing: China Electric Power Publishing House, 2006.
h
2-cold water side the coefficient of heat transfer (2000～7000) [W/ (m
2℃)], get 3000;
δ
1-heat exchanger plates thickness, (0.5～1.0mm), get 0.8;
δ
2-scale crust thickness is got 1.0mm, (0.5,1.0,1.5,2,0);
λ
1-heat exchanger plates thermal conductivity factor (85～50) [W/ (m ℃)] gets 120; Referring to: scape morning sunlight chief editor, the thermal technology is theoretical and use Beijing: China Electric Power Publishing House, 2004.
λ
2-incrustation scale thermal conductivity factor (1.28～3.14) [W/ (m ℃)] gets 1.50;
In above parameter substitution formula (1),
K＝{1/(13.79×10
-4)}
-1＝715.8[W/(m
2℃)]
If the hot water or cold water is the following current heat exchange in heat exchanger, cold water does not then have sediment incrustation through the online processing in electromagnetic field of high frequency, does not have the chemisorbed hard scale, δ yet
2=0, get heat-transfer area mud coefficient B
0=0.85, Coefficient K ' be then
K′＝B
0×(1/h
1+δ
1/λ
1+1/h
2)
-1 (2)
In top corresponding parameter substitution formula (2),
K′＝0.85/7.27×10
-4＝1169.2[W/(m
2℃)]
Thickness is that the heat output loss late η that the scale crust of 1.0mm causes is
η＝(K′-K)/K′＝38.8％
Find out that from table one antiscaling, descaling is the key technical problem that improves the plate type heat exchanger heat exchange efficiency.
Thermal conduction study about the logarithmic mean temperature difference (LMTD) formula of the cold and hot fluid following current heat exchange of heat exchanger is
Δt
mp＝(Δt
max-Δt
min)/ln(Δt
max/Δt
min) (3)
In the formula: Δ t
MpBe the heat exchanger mean temperature difference, Δ t
MaxWith Δ t
MinBe respectively the bigger and less end temperature difference of heat, cold fluid temperature approach at heat exchanger two ends, ℃; t
H1, t
H2Be respectively hot fluid import and outlet temperature, t
C1, t
C2Be respectively cold fluid import and outlet temperature.As Δ t
Min=t
H2-t
C2→ 0 o'clock (this is the actual conditions of plate type heat exchanger just), function Δ t
MpThere is singular point, can not correctly reflects the real physical process of plate type heat exchanger following current heat exchange.
The utility model content
The purpose of this utility model is to provide a kind of plate type heat exchanger that does not have sediment incrustation, fundamentally solves common plate type heat exchanger, and the plate-type heat-exchange unit that is composed in parallel by many platens formula heat exchanger, the problem of sediment incrustation and dirt between heat exchanger plates.
The technical solution of the utility model is:
A kind of plate type heat exchanger that does not have sediment incrustation, in the fixed pressure plate side of common plate type heat exchanger, the cold fluid import on fixed pressure plate top is connected with cold fluid return header road by pipeline; The cold fluid outlet of fixed pressure plate bottom goes out to flow total pipeline by pipeline and cold fluid and is connected.
The plate type heat exchanger of described no sediment incrustation is equipped with the High-frequency scale control descaling water disposal facility on cold fluid return header road.
The plate type heat exchanger of described no sediment incrustation is installed the High-frequency scale control descaling water disposal facility on hot fluid influent stream total pipeline.
The plate type heat exchanger of described no sediment incrustation is equipped with valve on the pipeline.
The plate type heat exchanger of described no sediment incrustation, plate type heat exchanger are in parallel use the more than two, constitute the plate-type heat-exchange unit of no sediment incrustation.
The heat exchange mode of the utility model heat exchanger is the following current heat exchange mode, and cold fluid enters from the cold fluid import on fixed pressure plate top, and flows out from the cold fluid outlet of fixed pressure plate bottom; Hot fluid enters from the hot fluid import on fixed pressure plate top, and flows out from the hot fluid outlet of fixed pressure plate bottom; The heat exchange process of cold and hot fluid in heat exchanger is the single process following current; Fluid diagonal angle between heat exchanger plates flows or monolateral flowing.
The utility model do not follow blindly that heat transfer theory points out " under identical outlet and inlet temperature, the Δ t of countercurrent flow
mValue is bigger than following current " guideline, referring to: [U.S.] Dai Weiaze Bel work, prince's health etc. is translated industrial process heat transfer applications, Beijing: Sinopec publishing house, 1992 years; And selected the following current heat exchange mode.Proved the heat exchanger theory of thermal conduction study about following current heat exchange logarithmic mean temperature difference (LMTD) formula Δ t by the utility model first
Mp=(Δ t
Max-Δ t
Min)/ln (Δ t
Max/ Δ t
Min), as Δ t
Min=t
H2-t
C2→ 0 o'clock (this is the truth of the plate type heat exchanger cold and hot fluid outlet temperature difference just), function Δ t
MpThere is singular point, causes Δ t
MpBig deviation appears in the result of calculation of formula in a big way.In order to correct following current logarithmic mean temperature difference (LMTD) formula, to the misleading of following current heat exchange, the utility model is according to similarity principle, with the equivalent single order R of fluid heat exchange for a long time
tC
tThe method for solving that series circuit responds fully, authenticated the uniformity of following current and countercurrent flow fluid temperature (F.T.) longshore current journey change curve, and the uniqueness of fluid temperature (F.T.) steady-state response, and " the μ converter technique " of deducing out the following current heat exchange, with the mean temperature difference problem of following current heat exchange, be transformed into countercurrent flow logarithmic mean temperature difference (LMTD) problem and handle.The utility model provides plate type heat exchanger following current heat exchange mean temperature difference Δ t
MpComputational methods be: with fluid temperature (F.T.) longshore current journey change curve through " μ conversion " afterwards, can adopt countercurrent flow logarithmic mean temperature difference (LMTD) Δ t fully
McComputational methods, work as t
H1-t
C2＞t
H2-t
C1The time, Δ t
Max=t
H1-t
C2, Δ t
Min=t
H2-t
C1Work as t
H1-t
C2＜t
H2-t
C1The time, Δ t
Max=t
H2-t
C1, Δ t
Min=t
H1-t
C2Δ t then
Mp=Δ t
Mc=(Δ t
Max-Δ t
Min) ln (Δ t
Max/ Δ t
Min); Work as t
H1-t
C2=t
H2-t
C1The time, Δ t then
Mp=t
H1-t
C2Wherein: Δ t
MpBe the heat exchanger mean temperature difference, Δ t
MaxWith Δ t
MinBe respectively the bigger and less end temperature difference of heat, cold fluid temperature approach at heat exchanger two ends, ℃; t
H1, t
H2Be respectively hot fluid import and outlet temperature, t
C1, t
C2Be respectively cold fluid import and outlet temperature.
The beneficial effects of the utility model are:
(1) the utility model is by changing the existing common plate type heat exchanger cold fluid import and the conventional connected mode of outlet conduit, realize no sediment incrustation, cold and hot fluid flows in heat exchanger from top to down, be the following current heat exchange mode, by percussion and the effect of scale particles self gravitation that cold and hot fluid flows from top to down, realize " zero-emission " and online " automatic pollution discharge " function of plate type heat exchanger in heat exchanger.The utility model can play corrects thermal conduction study heat exchanger theory for a long time to the misleading effect of plate type heat exchanger following current heat exchange, thereby finishes " heat exchanger adopts counter-flow arrangement as far as possible " as early as possible and an innocent person who causes wastes the history of ample resources;
(2) the utility model plate type heat exchanger adopts the work of following current heat exchange mode, regularly blowdown, real " zero-emission ", the conserve water resource of realizing; No sediment incrustation and dirt in the heat exchanger improve heat exchange efficiency, fuel savings and power resource;
(3) because the reasonability of following current heat exchange mode, the utility model plate type heat exchanger can use the water of general hardness to replace demineralized water, has both improved heat exchange efficiency, reduces operating cost again, therefore, the utility model plate type heat exchanger enters civilian heating station station replacement boiler heat supplying becomes possibility; To reducing CO
2Pollute with dust fall, improve the ecological environment, positive effect is arranged;
(4) the utility model plate type heat exchanger is by installing the High-frequency scale control descaling water disposal facility on cold fluid return header road, perhaps, the High-frequency scale control descaling water disposal facility is installed on hot fluid influent stream total pipeline again, then can receive the operational effect of using demineralized water, both there be not sediment incrustation and dirt in the heat exchanger, the hard scale that does not have chemisorbed again can be realized the highest heat exchange efficiency, minimum operating cost and minimum labour intensity.
(5) the utility model has proved the logarithmic mean temperature difference (LMTD) formula of the heat exchanger theory of thermal conduction study about the following current heat exchange, is not suitable for modern plate type heat exchanger, for a long time the following current heat exchange is misled the huge waste that causes to human resource thereby finish it.
(6) in the utility model cancellation traditional design, the sewage draining valve that sewage draining valve that the cold fluid outlet on fixed pressure plate top is provided with and the hot fluid outlet in the fixed pressure plate bottom are provided with.
Description of drawings
Fig. 1, the utility model do not have fluid inlet, the outlet conduit connection diagram of the plate type heat exchanger of sediment incrustation;
The fluid inlet of the common plate type heat exchanger of Fig. 2, current trend, outlet conduit connection diagram;
Fig. 3, cold and hot fluid under import and outlet temperature same case, the logarithmic mean temperature difference (LMTD) curve map of following current and countercurrent flow;
The superposition principle figure that Fig. 4 (a)-(c), single order RC series circuit respond fully; (a) for responding u fully
c(0)=U
0(b) be zero state response u
Ce(0)=0; (c) be zero input response u
Cf(0)=U
0
Fig. 5 (a)-(c), plate type heat exchanger equivalence single order R
tC
tThe superposition principle figure that series circuit responds fully; (a) for responding t fully
f(0)=t
H1(0) or t
C1(0); (b) be zero state response t
Fe(0)=0; (c) be zero input response t
Ff(0)=t
H1(0) or t
C1(0);
Fig. 6, single order RC series circuit respond capacitance voltage u fully
c(t) curve map;
Fig. 7, equivalent single order R
tC
tThe complete fluid-responsive temperature t of series circuit
f(A) curve map;
Fig. 8, following current heat exchanging fluid temperature are along the μ conversion schematic diagram of journey change curve;
Fig. 9, the plate-type heat-exchange unit sketch of High-frequency scale control descaling water disposal facility is installed.
Among the figure, 1. plate type heat exchanger; 2. fixed pressure plate; 21. cold fluid import; 22. hot fluid import; 23. cold fluid outlet; 24. hot fluid outlet; 3,4. connecting pipe; 5,6. valve; 7. cold fluid return header road; 8. cold fluid goes out to flow total pipeline; 9. High-frequency scale control descaling water disposal facility; 10. sewage draining valve; 11. hot fluid influent stream total pipeline; 12. hot fluid goes out to flow total pipeline; A. heat exchange area; C. electric capacity; C
t. the fluid thermal capacitance; K. switch; R. resistance; R
t. thermal resistance; T. time; t
C1. the cold fluid inlet temperature; t
C2. the cold fluid outlet temperature; t
f. fluid temperature (F.T.); t
Fe. the nought state temperature; t
Ff. zero input temp; t
m. the fluid steady temperature; t
H1. the hot fluid inlet temperature; t
H2. the hot fluid outlet temperature; Δ t
Mc. the countercurrent flow logarithmic mean temperature difference (LMTD); Δ t
Mp. following current heat exchange logarithmic mean temperature difference (LMTD); Δ t
MaxBe the bigger end temperature difference of heat, the cold fluid temperature approach at heat exchanger two ends; Δ t
MinBe the less end temperature difference of heat, the cold fluid temperature approach at heat exchanger two ends.
The specific embodiment
Embodiment 1
As shown in Figure 1, in fixed pressure plate 2 sides of common plate type heat exchanger 1, with the pipeline 3 of valve 5 is installed, the cold fluid import 21 on fixed pressure plate 2 tops is connected with cold fluid return header road 7; With the pipeline 4 that valve 6 is installed, the cold fluid of fixed pressure plate 2 bottoms outlet 23 is gone out to flow total pipeline 8 with cold fluid be connected, hot fluid import 22 communicates with hot fluid influent stream total pipeline 11, and hot fluid exports 24 and goes out to flow total pipeline 12 with hot fluid and communicate.This pipeline connection features is when valve 5 and valve 6 during for opening, can make the cold fluid in the return header road 7, flow to the plate type heat exchanger 1 from the cold fluid import 21 on fixed pressure plate 2 tops, cold fluid flows in heat exchanger from top to down, carry out after the following current heat exchange with hot fluid, flow out from the cold fluid outlet 23 of fixed pressure plate 2 bottoms again, enter out stream total pipeline 8.In existing, the low pressure plate type heat exchanger almost without exception, hot fluid all is that the hot fluid import 22 from fixed pressure plate 2 tops flows to the plate type heat exchanger 1, flow from top to down, after the cold fluid heat exchange, flow out from the hot fluid outlet 24 of fixed pressure plate 2 bottoms.The utility model purpose is the percussion and the effect of scale particles self gravitation of flowing from top to down in plate type heat exchanger by cold and hot fluid, realize " zero-emission " and online " automatic pollution discharge " function of plate type heat exchanger, reach the optimum operation purpose of interior no sediment incrustation of plate type heat exchanger and dirt.If cold fluid is not through the softening water of handling, so in heat transfer process, also can on the heat exchanger plates of cold flow side, generate the hard scale of chemisorbed inevitably, the thickness of hard scale layer changes along with the carbonate total hardness of fluid, only can only remove the sediment incrustation of physical absorption with the following current heat exchange, be can not the full scale clearance chemisorbed hard scale.Usually hot fluid all is to use the demineralized water of handling through softening, does not tie hard scale basically.For fear of on heat exchanger plates, generating hard scale, can adopt the scheme of the utility model embodiment 2.
Embodiment 2
As shown in Figure 9, on the basis of embodiment 1 described cold and hot fluid following current heat exchange, again on cold fluid return header road 7, a High-frequency scale control descaling water disposal facility 9 that provides as utility model patent ZL96 2 38603.0 is installed, even cold fluid is the higher underground water of hardness ratio like this, can not tie hard scale on the heat exchanger plates, can reach had not both had sediment incrustation, did not tie the purpose of hard scale again yet.Fig. 9 is many platens formula heat exchangers in parallel structure, cold fluid import 21 communicates with cold fluid return header road 7 respectively, hot fluid import 22 communicates with hot fluid influent stream total pipeline 11 respectively, cold fluid outlet 23 goes out to flow total pipeline 8 with cold fluid respectively and communicates, and hot fluid outlet 24 goes out to flow total pipeline 12 with hot fluid respectively and communicates.
Embodiment 3
Embodiment 2 described installations on the cold fluid return header road 7 on the basis of High-frequency scale control descaling water disposal facility, a High-frequency scale control descaling water disposal facility that provides as utility model patent ZL96 2 38603.0 is installed on hot fluid influent stream total pipeline 11 again, cold and hot fluid can be used non-demineralized water like this, can realize both not had sediment incrustation and dirt in the plate type heat exchanger, not have the hard scale of chemisorbed again.
The utility model proposes a kind of constructive method that does not have the plate type heat exchanger of sediment incrustation, by changing the existing common plate type heat exchanger cold fluid import and the conventional connected mode of outlet conduit, promptly, make the conventional location swap that connects import and outlet conduit, change the conventional flow direction of cold fluid in heat exchanger, make cold originally, the hot fluid countercurrent flow, become the following current heat exchange, by cold, percussion and the effect of scale particles self gravitation that hot fluid flows in heat exchanger from top to down, realize " zero-emission " and online " automatic pollution discharge " function of plate type heat exchanger, reach no sediment incrustation in the heat exchanger, energy-conservation, water saving, save the purpose of resource.
The heat exchanger theory that the utility model has been proved thermal conduction study about " cold and hot fluid under import and outlet temperature same case, reverse-flow logarithmic mean temperature difference (LMTD) Δ t
mGreater than downflow type " conclusion be incorrect for plate type heat exchanger; The utility model has pointed out to cause following current heat exchange logarithmic mean temperature difference (LMTD) formula Δ t
MpThe reason that calculation deviation is big is that the function that characterizes this formula exists singular point Δ t
Min, be not suitable for plate type heat exchanger; The utility model applications similar principle has authenticated the uniformity of following current and countercurrent flow fluid temperature (F.T.) longshore current journey change curve, and the uniqueness of fluid temperature (F.T.) steady-state response, and then " the μ converter technique " of deducing out the following current heat exchange, promptly following current heat exchange temperature longshore current journey change curve is transformed to the countercurrent flow temperature journey change curve of equivalence, rationally avoids function singular point Δ t
Min, with countercurrent flow logarithmic mean temperature difference (LMTD) formula Δ t
McCalculate the mean temperature difference Δ t of following current heat exchange
MpProblem.
(a) there is singular point in the logarithmic mean temperature difference (LMTD) formula of following current heat exchange, and the heat flow formula that it is not suitable for the plate type heat exchanger thermal conduction study is
Q＝KAΔt
m (4)
Q in the formula: heat flow, W; K: plate type heat exchanger overall heat-transfer coefficient, W/ (m
2℃); A: heat exchange area, m
2Δ t
m: the logarithmic mean temperature difference (LMTD) of cold fluid and hot fluid, ℃ (contrary, following current heat exchange logarithmic mean temperature difference (LMTD) formula Δ t
mForm is identical, and footnote c, p represent contrary, following current respectively).Cold and hot fluid heat exchange power (heat flow) and Δ t
mBe directly proportional, thermal conduction study provides
Δt
m＝(Δt
max-Δt
min)/ln(Δt
max/Δt
min) (5)
In the formula, Δ t
MaxWith Δ t
MinBe respectively the bigger and less end temperature difference of heat, cold fluid temperature approach at heat exchanger two ends, ℃.When adverse current: if t
H1-t
C2＞t
H2-t
C1, Δ t then
Max=t
H1-t
C2, Δ t
Min=t
H2-t
C1If t
H1-t
C2＜t
H2-t
C1, Δ t then
Max=t
H2-t
C1, Δ t
Min=t
H1-t
C2If t
H1-t
C2=t
H2-t
C1, Δ t then
Mc=t
H1-t
C2When following current: Δ t
Max=t
H1-t
C1, Δ t
Min=t
H2-t
C2t
H1, t
H2Be respectively hot fluid import and outlet temperature, t
C1, t
C2Be respectively cold fluid import and outlet temperature.
Logarithmic mean temperature difference (LMTD) Δ t at heat exchanger
mIn the derivation, after the variables separation integration,
Δt
x＝Δt
maxexp(-μKA
x)
It is push away the important function formula of logarithmic mean temperature difference (LMTD) formula.Work as A
xDuring → A, Δ t
x→ Δ t
Min, then have
Δt
min＝Δt
maxexp(-μKA) (6)
When adverse current: μ=(1/m
1C
1-1/m
2C
2)=μ
1-μ
2, μ
1=1/m
1C
1, μ
2=1/m
2C
2When following current: μ '=(1/m
1C
1+ 1/m
2C
2)=μ
1+ μ
2In the formula, m
1: hot fluid mass flow, Kg/S; m
2: cold fluid mass flow, Kg/S; C
1: hot fluid specific heat, Kj/Kg ℃; C
2: cold fluid specific heat, Kj/Kg ℃; K: heat transfer coefficient, [W/m
2℃]; A: heat exchange area, m
2
From physical unit, μ and μ ' be hot temperature equivalent (℃/W), be the physical quantity that characterizes fluid temperature (F.T.) longshore current journey variation tendency, the various heat exchange area of the corresponding heat exchanger of each point coordinates on the flow process.
Under the countercurrent flow situation, hot fluid temperature longshore current journey is the attenuation change rule in formula (6) the description heat transfer process, and cooling fluid temperature adverse current journey is the attenuation change rule, works as μ
1＞μ
2The time, two temperature variation curves are approaching gradually; Work as μ
1＜μ
2The time, two temperature variation curves separate gradually; Work as μ
1=μ
2The time, two temperature variation curves are straight lines parallel to each other.During countercurrent flow, Δ t
Min=t
H2-t
C1Perhaps Δ t
Min=t
H1-t
C2Usually all non-vanishing.Therefore, countercurrent flow logarithmic mean temperature difference (LMTD) formula does not have about singular point.
Under following current heat exchange situation, formula (6) is described cold and hot fluid temperature longshore current journey and is growth and attenuation change rule respectively.μ no matter
1And μ
2Quantitative relation how, and two temperature variation curves of cold and hot fluid all are approaching fast, i.e. Δ t
Min=Δ t
Max(μ ' KA) decay is very fast, Δ t for exp
MinGo to zero fast.It is to cause following current heat exchange logarithmic mean temperature difference (LMTD) formula the reason of singular point to occur.Logarithm factor ln (Δ t in the formula (5)
Max/ Δ t
Min), at Δ t
Min→ 0 o'clock, logarithm was not restrained, and made Δ t
MpFunctional value be 0.Plate type heat exchanger is operated under water-water following current heat exchange situation, this just situation, Δ t
Min=t
H2-t
C2Almost nil, cause Δ t
MpNear formula misalignment in sizable zone singular point.
In following table,, come comparison logarithmic mean temperature difference (LMTD) formula, when the following current heat exchange, because function Δ t with several groups of data that the cold and hot fluid import is identical with outlet temperature
MpThere is singular point, causes result of calculation to depart from the order of severity of actual conditions.
Downflow type and reverse-flow logarithmic mean temperature difference (LMTD) comparison sheet when table two hot water or cold water (water-water) import is identical with outlet temperature
In the last table,
*Singular point causes the zone that deviation is big;
*Singular point does not have the influence area substantially.
Find out from table two and Fig. 3, at Δ t
Min→ 0, near the function singular point in a big way in, following current logarithmic mean temperature difference (LMTD) Δ t
MpMuch smaller than adverse current logarithmic mean temperature difference (LMTD) Δ t
Mc, i.e. Δ t
Mp＜＜Δ t
McAs Δ t
MinDuring → ∞, away from the function singular point, Δ t
Mp→ Δ t
Mc, i.e. Δ t
Min=t
H2-t
C2The temperature difference is big more, Δ t
MpApproach Δ t more
McThis variation tendency shows, at Δ t
MinAway from function singular point zone, suitable, adverse current logarithmic mean temperature difference (LMTD) formula Δ t
MpWith Δ t
McBe equivalent, this characteristic is the key of technical solution problem.
(b) according to similarity principle, with equivalent single order R
tC
tThe method for solving that series circuit responds is fully asked for the response fully of plate type heat exchanger fluid temperature (F.T.)
Similarity principle is applied among the research of the various similar physical phenomenons of natural science widely, and there is atomic wonderful duality relation in some physical quantity of thermal conduction study and electricity.With ask for Δ t
mRelevant corresponding physical quantity is listed in the table three.
Some corresponding physical quantity of table three thermal conduction study and electricity
| The thermal conduction study amount | Steady temperature t m，℃ | Thermal resistance r t，m 2℃/W | Heat flow Q, W | Thermal capacity C t，Kj/℃ | Fluid temperature (F.T.) t f(A)，℃ |
| Electrical quantities | Supply voltage U s，V | Resistance R, ρ L/m 2 | Electric current I, A | Capacitor C, q/V | Capacitance voltage u c(t)，V |
The Newton's law of cooling of thermal conduction study: Q=t
m/ R
t, the Ohm's law of corresponding electricity: I=U
s/ R; This two formula is one of the foundation of applications similar principle just.
The equivalent circuit structure of plate type heat exchanger heat transfer correspondence is similar to single order RC series circuit, and the effective area of establishing heat exchanger is A, and entire thermal resistance is R
t, the temperature of fluid is t
f(A), mass flow is respectively m
1And m
2, the homogeneity specific heat capacity is C
1=C
2
The applications similar principle, the superposition principle Fig. 4 (a)-(c) that responds fully from single order RC series circuit; Wherein, (a) for responding u fully
c(0)=U
0, (b) be zero state response u
Ce(0)=0, (c) for zero input response U
Cf(0)=U
0, Fig. 4 (a) is the stack of Fig. 4 (b) and Fig. 4 (c), U
0Be the initial voltage of capacitor C, u
Ce(0) is the initial voltage of zero state response capacitor C, u
Cf(0) for the initial voltage of zero input response capacitor C.Capacitor C voltage u
cSeparating as shown in Figure 6 (t) worked as U
s＞U
0The time, u
c(t) corresponding curve 1; Work as U
s＜U
0The time, u
c(t) corresponding curve 2; Work as U
s=U
0The time, u
c(t) corresponding curve 3; And then the heat exchanger heat transfer equivalence single order R that deduces out correspondence
tC
tSuperposition principle Fig. 5 that series circuit responds fully (a)-(c); Among the figure, (a) for responding t fully
f(0)=t
H1(0) or t
C1(0); (b) be zero state response t
Fe(0)=0; (c) be zero input response t
Ff(0)=t
H1(0) or t
C1(0); Fig. 5 (a) is the stack of Fig. 5 (b) and Fig. 5 (c), t
f(0) represents the initial temperature of fluid, t
Fe(0) represents nought state temperature, t
Ff(0) representative zero input temp.
Single order R
tC
tSeries circuit responds equivalence fully and is zero state response and zero input response superposition mutually, and its differential equation that conducts heat correspondence is
R
tC
t·d[t
f(A)]/dA+t
f(A)＝t
m (7)
The initial temperature of fluid is t
f(0)=t
h(0) or t
c(0); When A=0, the K switch closure.
The differential equation separate t
f(A) by particular solution t
f(A) ' and general solution t
f(A) " form, i.e. t
f(A)=t
f'+t
f", particular solution t
f'=t
m, general solution t
f"=Be
-A/ τ t+ t
m, τ in the formula
t=R
tC
t
According to primary condition, get integral constant B=t
f(0)-t
m, then
t
f(A)＝t
f′+t
f″＝[t
f(0)-t
m]e
-A/τt+t
m (8)
First on formula (8) the right is that transient state is separated, or claims transient response.Work as t
f(0)＞t
mThe time, t
f(0)=t
H1, the inlet temperature of expression hot fluid, what transient state was separated description is the hot fluid exothermic process, from inlet temperature t
H1Begin to decay to outlet temperature t by index law
H2, transient response attenuation curve, corresponding diagram 7 curves 2; Work as t
f(0)＜t
mThe time, t
f(0)=t
C1, the inlet temperature of expression cold fluid, what this moment, transient state was separated description is the cold fluid endothermic process, from inlet temperature t
C1Begin to rise to outlet temperature t by index law
C2, transient response growth curve corresponding diagram 7 curves 1; Work as t
f(0)=t
mThe time, expression cold and hot fluid inlet temperature is identical, i.e. t
H1=t
C1=t
m, what this moment, transient state was separated description is that the cold and hot fluid temperature is identical, the exchange of heat transfer process empty calory, transient response corresponding diagram 7 straight lines 3.
Second on formula (8) the right is a steady state solution, or claims steady-state response.t
mBe that hot fluid is finished exothermic process, the end value of exit temperature, i.e. t
H2→ t
mIt also can be that cold fluid is finished endothermic process, the end value of exit temperature, i.e. t
C2→ t
m
The heat transfer differential equation of first order is separated t
f(A) and the curve among Fig. 71,2 and 3, the heat exchange physical process of cold and hot fluid in plate type heat exchanger intactly described.For the parameter combinations of any cold and hot fluid heat exchange that may exist, no matter the transient state of the differential equation is separated, or steady state solution all is well-determined.
(c) acquiring method of following current heat exchange mean temperature difference
The expression formula of μ and μ ' is compared in examination, and the two difference only is μ
2Sign, if change μ
2Symbol, just can realize the conversion between following current and the countercurrent heat exchange method.In order to eliminate the calculation deviation that following current heat exchange logarithmic mean temperature difference (LMTD) function singular point causes, so introducing following transform method: Fig. 7 is equivalent single order R
tC
tThe complete fluid-responsive temperature t of series circuit
f(A) curve map at the curve 1 of Fig. 7 and 2 point, is about 3 τ
t(=3R
tC
t, get it in the engineering calculation and be the final value of e index) and the position gets 1 A, and the A point is positioned on the straight line 3, crosses the vertical line that the A point is made straight line 3, with 180 ° of curve 1 flip horizontals, makes the starting point t of curve 1
C1Dropped on the vertical line that A orders.So just finished following current heat exchanging fluid temperature longshore current journey change curve, be converted to countercurrent flow fluid temperature (F.T.) longshore current journey change curve, be called for short " warm Cheng Bianhuan " or " μ conversion " (see figure 8).Fig. 8 is the conversion schematic diagram of following current and countercurrent flow fluid temperature (F.T.) longshore current journey change curve.It is the simplest " coordinate system-territory " conversion that this transform method can be understood as, and its transformation factor is e
-μ KAIn μ, from the μ=1/m in following current territory
1C
1+ 1/m
2C
2, transform to the μ=1/m of reverse-flow region
1C
1-1/m
2C
2Thereby, the mean temperature difference Δ t in following current territory
Mp, can use the logarithmic mean temperature difference (LMTD) formula of reverse-flow region
Δt
mc＝(Δt
max-Δt
min)/ln(Δt
max/Δt
min)
Calculate; Wherein, work as t
H1-t
C2＞t
H2-t
C1The time, Δ t
Max=t
H1-t
C2, Δ t
Min=t
H2-t
C1Work as t
H1-t
C2＜t
H2-t
C1The time, Δ t
Max=t
H2-t
C1, Δ t
Min=t
H1-t
C2In the plate type heat exchanger field, with the import and the outlet temperature of the cold and hot fluid of following current heat exchange, be transformed to the import and the outlet temperature of corresponding countercurrent flow, carry out logarithmic mean temperature difference (LMTD) and calculate, eliminated the calculation deviation that the function singular point causes.Thereby, can correct plate type heat exchanger following current heat exchange logarithmic mean temperature difference (LMTD) theoretical formula, for a long time to the misleading of following current heat exchange.
Claims (5)
1, a kind of plate type heat exchanger that does not have sediment incrustation is characterized in that: fixed pressure plate (2) side in common plate type heat exchanger (1), and the cold fluid import (21) on fixed pressure plate (2) top is connected with cold fluid return header road (7) by pipeline (3); The cold fluid outlet (23) of fixed pressure plate (2) bottom goes out to flow total pipeline (8) by pipeline (4) and cold fluid and is connected.
2, according to the plate type heat exchanger of the described no sediment incrustation of claim 1, it is characterized in that: High-frequency scale control descaling water disposal facility (9) is installed on cold fluid return header road (7).
3, according to the plate type heat exchanger of claim 1 or 2 described no sediment incrustations, it is characterized in that: the High-frequency scale control descaling water disposal facility is installed on hot fluid influent stream total pipeline.
4, according to the plate type heat exchanger of the described no sediment incrustation of claim 1, it is characterized in that: valve (5) is installed on the pipeline (3); Valve (6) is installed on the pipeline (4).
5, according to the plate type heat exchanger of the described no sediment incrustation of claim 1, it is characterized in that: plate type heat exchanger is in parallel more than two, constitutes the plate-type heat-exchange unit of no sediment incrustation.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200620091827 CN200965443Y (en) | 2006-06-30 | 2006-06-30 | A non-depositional scale plate type heat exchanger |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200620091827 CN200965443Y (en) | 2006-06-30 | 2006-06-30 | A non-depositional scale plate type heat exchanger |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104006683A (en) * | 2014-05-01 | 2014-08-27 | 铜陵钱谊化工设备有限责任公司 | Plate heat exchanger |
-
2006
- 2006-06-30 CN CN 200620091827 patent/CN200965443Y/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104006683A (en) * | 2014-05-01 | 2014-08-27 | 铜陵钱谊化工设备有限责任公司 | Plate heat exchanger |
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Granted publication date: 20071024 Termination date: 20110630 |