Heat exchange carbon control design method based on refrigerant GWP value

Abstract

The invention discloses a heat exchange carbon control design method based on a refrigerant GWP value, and relates to the technical field of fire safety. According to an ecological design method of a regenerative heat exchange tube based on the refrigerant GWP value, firstly, a carbon footprint energy efficiency value serves as a design index when the regenerative heat exchange tube is designed; the carbon emission amount of a refrigerating system where the regenerative heat exchange pipe is located can reach the controllable amount within a certain time range, the carbon emission requirement of the ecological environment is met, on the premise that the carbon emission requirement of the ecological environment is followed, the qualitative temperature of the condenser side and the qualitative temperature of the evaporator side are calculated firstly, and the physical property parameters of fluid on the two sides are obtained; calculating the heat exchange amount and the countercurrent logarithmic average temperature difference, estimating the heat transfer area of a backheating heat exchange pipe, preliminarily estimating and selecting the pipes on the two sides and specifications, adjusting the parameters of the pipes on the two sides and the specifications by evaluating the pressure drop on the two sides, and calculating the heat transfer area of the backheating heat exchange pipe on the premise that the pressure drop standard conditions of the pipes on the two sides are met. And the real heat transfer area parameter range of the regenerative heat exchange tube is continuously considered, so that the heat exchange efficiency of the regenerative heat exchange tube is greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of heat recovery and heat exchange, and in particular to a heat exchange carbon control design method based on the GWP value of a refrigerant. Background Art

[0002] With the development of economy, heat exchange tubes play an increasingly important role in the field of refrigeration and are more and more widely used. Therefore, the design requirements for heat exchange tubes are becoming more and more stringent. General production design often ignores the ecological problems caused by the carbon emissions of refrigerants during the operation of heat exchange tubes. Secondly, the heat exchange efficiency of existing heat exchange tubes inside and outside the tube is not high. How to improve the heat exchange by designing the structure of the heat exchange tube is also a difficulty in the current design of heat exchange tubes. Summary of the invention

[0003] In order to overcome the above-mentioned problem of how to consider the ecological environment in the prior art while improving the structure of the heat recovery heat exchange tube to improve heat exchange, the present invention proposes a heat exchange carbon control design method and device based on the GWP value of the refrigerant.

[0004] To achieve the above object, the present invention adopts the following technical solution, a heat exchange carbon control design method based on the GWP value of the refrigerant, comprising:

[0005] S1: Select the type of refrigerant and determine the GWP of the refrigerant, where GWP is the global warming potential;

[0006] S2: Calculate the carbon footprint energy efficiency value G based on the refrigerant;

[0007] S3: Determine whether the carbon footprint value C and the refrigeration system energy efficiency value EER are compatible, that is, whether the carbon footprint energy efficiency value G meets the preset standard. If yes, proceed to the next step. Otherwise, adjust the subcooling degree of the heat exchange tube so that the carbon footprint energy efficiency value G meets the preset standard, and then proceed to the next step.

[0008] S4: Based on the basic data on the condenser side and the evaporator side, determine the heat transfer Q of the heat exchange tube and the countercurrent logarithmic mean temperature difference △t m ;

[0009] S5: Based on heat transfer Q and counterflow logarithmic mean temperature difference △t m Estimate the heat transfer area A, select the pipe materials and specifications on both sides, and calculate the pressure drop △P on the evaporator side i and condenser side pressure drop △P L ;

[0010] S6: Determine whether the pressure drop on the evaporator side and the pressure drop on the condenser side meet the standard conditions. If the pressure drop on the evaporator side does not meet the standard conditions, reselect the pipe material and specifications on the evaporator side. If the pressure drop on the condenser side does not meet the standard conditions, reselect the pipe material and specifications on the condenser side. If the pressure drops on both sides meet the standard conditions, proceed to the next step.

[0011] S7: Calculate the actual heat transfer area A based on the heat transfer coefficient on the evaporator side and the heat transfer coefficient on the condenser side ” and the actual tube length l', determine the actual heat transfer area A ” Does the heat transfer area A' satisfy k1·A"≤A'≤k2·A"? If yes, it proves that the above evaporator side structure and condenser side structure are reasonably designed, and the design result of the heat recovery heat exchange tube is obtained; if no, it jumps to step S5, where 0.9 <k1<k2<1.5。

[0012] A heat recovery heat exchange tube device is suitable for a heat exchange carbon control design method based on the GWP value of a refrigerant, comprising: a heat recovery heat exchange tube, a casing is arranged inside the heat recovery heat exchange tube, and the casing adopts an internal thread structure; an evaporator interface tube is arranged on one side of the heat recovery heat exchange tube, the evaporator interface tube is a pipe without an elbow, and is connected to the evaporator inlet; a condenser interface tube is arranged on the other side of the heat recovery heat exchange tube, the condenser interface tube is a pipe with an elbow, and is connected to the condenser outlet; on the heat recovery heat exchange tube, a throttle valve interface is arranged between the condenser interface tube and the evaporator interface tube, which is used to connect to the throttle valve so that the refrigerant from the condenser flows to the throttle valve.

[0013] The advantages of the present invention are:

[0014] (1) The present invention uses the carbon footprint energy efficiency value as a design indicator when designing the heat recovery heat exchange tube. On the one hand, the carbon emissions of the refrigeration system where the heat recovery heat exchange tube is located can reach a controllable amount within a certain time range, meeting the carbon emission requirements of the ecological environment, helping to mitigate climate change, protect the ecological environment, and support long-term sustainable development goals. On the other hand, it also provides a new and more ecological design idea and solution for the design of the heat recovery heat exchange tube, that is, the design must be based on ecology and also comply with the increasingly stringent environmental protection and energy efficiency regulations and standards around the world.

[0015] (2) The design method of the heat exchanger tube of the present invention designs the condenser side and evaporator side pipes of the heat exchanger tube on the premise of complying with the ecological environment carbon emission requirements. On the premise of meeting the standard conditions of the pressure drop of the pipes on both sides, the actual heat transfer area parameter range of the heat exchanger tube is continued to be considered, thereby greatly improving the heat exchange efficiency of the heat exchanger tube.

[0016] (3) Under the premise of complying with the ecological environment carbon emission requirements, the design method of the heat exchange tube of the present invention first calculates the qualitative temperature of the condenser side and the evaporator side to obtain the physical properties of the fluids on both sides, then calculates the heat transfer amount and the countercurrent logarithmic mean temperature difference, estimates the heat transfer area of ​​the heat exchange tube, and then makes a preliminary assessment of the tube materials and specifications on both sides. By evaluating the pressure drop on both sides, the tube materials and specification parameters on both sides are adjusted, thereby making the design of the heat exchange tube more reasonable and accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the working flow diagram of the refrigeration system;

[0018] Figure 2 This is the appearance diagram of the internally threaded heat recovery heat exchange tube;

[0019] Figure 3 It is a cross-sectional view of the internal threaded pipe structure;

[0020] Figure 4 It is a schematic diagram of the cross section of an internally threaded pipe;

[0021] Figure 5 Schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] like Figure 1-2 As shown, the first aspect of the present invention proposes a heat recovery heat exchange tube device, comprising: a heat recovery heat exchange tube, a sleeve is arranged inside the heat recovery heat exchange tube, the sleeve adopts an internal thread structure, a heat exchange carbon control design method based on the GWP value of the refrigerant is used to select the type of refrigerant and the GWP (global warming potential) is preliminarily selected for the internal thread structure parameters, and then the final value of the internal thread parameter is finally determined through iterative correction calculation; an evaporator interface pipe is arranged on one side of the heat recovery heat exchange tube, and the evaporator interface pipe is a small diameter pipe without an elbow, which is connected to the evaporator The inlet is connected, and for the convenience of connection, the pipe length of the evaporator interface pipe can be adjusted according to actual use; a condenser interface pipe is provided on the other side of the heat recovery heat exchange pipe, and the condenser interface pipe is a small-diameter pipe with an elbow, which is connected to the condenser outlet. For the convenience of connection, the elbow angle and the pipe length can be adjusted according to actual use; on the heat recovery heat exchange pipe, a throttle valve interface is provided between the condenser interface pipe and the evaporator interface pipe, which is used to connect with the throttle valve so that the refrigerant from the condenser flows to the throttle valve.

[0024] The second aspect of the present invention provides a heat exchange carbon control design method based on the GWP value of the refrigerant, which is to design the heat exchange tube on the premise of achieving the rated standard carbon emission. It includes:

[0025] S1: Select the type of refrigerant and determine the GWP of the refrigerant;

[0026] S2: Calculate the carbon footprint energy efficiency value G based on the basic data of the refrigerant and the heat exchange tube condenser side. The formula is:

[0027]

[0028] Among them, C is the carbon footprint value, EER is the energy efficiency value of the refrigeration system, Q L is the amount of refrigerant used, S is the refrigerant leakage rate, GWP is the global warming potential, which is determined according to the type of refrigerant, a is the operating years, and COP is the refrigeration coefficient, which is calculated by the calculation software.

[0029] The basic data on the condenser side include the condenser side inlet temperature t1, the subcooling degree △t1, and the condenser side outlet temperature t1'; wherein t1'=t1-△t1.

[0030] S3: Determine whether the carbon footprint value C and the refrigeration system energy efficiency value EER are compatible, that is, whether the carbon footprint energy efficiency value G meets the preset standard. If so, proceed to the next step. Otherwise, adjust the subcooling of the heat exchange tube. By adjusting the subcooling, the refrigeration system energy efficiency value EER is adjusted to make the carbon footprint energy efficiency value G meet the preset standard. That is, the carbon footprint value C and the refrigeration system energy efficiency value EER are compatible, ensuring the dynamic balance between the two, and then proceed to the next step.

[0031] Among them, the pre-set standards are refrigerants with GWP ranges of 0-150, 150-1500, and >1500, and the corresponding standard ranges of carbon footprint energy efficiency values ​​G are ≤10kg·a, ≤90kg·a, and ≤245kg·a, respectively.

[0032] S4: Based on the basic data on the condenser side and the basic data on the evaporator side, determine the qualitative temperature t of the condenser side (shell side) of the heat exchange tube 1p and the qualitative temperature t of the evaporator side (tube side) 2p , obtain the physical parameters of the refrigerant fluid on both sides (shell side and tube side), as well as the heat transfer Q and the countercurrent logarithmic mean temperature difference △t m ,include:

[0033] Among them, the basic data on the evaporator side include the evaporator side inlet temperature t2, the evaporator side outlet temperature t2', the superheat △t2, and the physical properties of the refrigerant fluid include the qualitative temperature of the condenser side and the evaporator side, the refrigerant specific heat of the condenser side and the evaporator side, the refrigerant dynamic viscosity of the condenser side and the evaporator side, the refrigerant thermal conductivity of the condenser side and the evaporator side, the refrigerant Prandtl number of the condenser side and the evaporator side, and the refrigerant density of the condenser side and the evaporator side.

[0034] S41: Calculate the qualitative temperature of the condenser side, the qualitative temperature of the condenser side t 1p The calculation formula is:

[0035]

[0036] S42: determining the physical property parameters of the refrigerant fluid based on the qualitative temperature on the condenser side;

[0037] S43: Determine the heat exchange amount Q based on the physical parameters of the refrigerant fluid. The heat exchange amount Q is calculated as follows:

[0038] Q=q1=q2=c p1 .q m .△t1

[0039] q1 is the heat exchange on the condenser side, q2 is the heat exchange on the evaporator side, c p1 is the specific heat of the refrigerant on the condenser side, q m is the refrigerant mass flow rate, obtained by computer software;

[0040] S44: Obtain superheat △t2 based on the heat exchange, c p2 is the specific heat of the refrigerant on the evaporator side, and the outlet temperature on the evaporator side is t2'=t2+△t2;

[0041] The qualitative temperature of the evaporator side needs to be assumed first. First, assume that the inlet temperature t2 of the evaporator side is the qualitative temperature of the evaporator side, and query the physical properties of the refrigerant on the evaporator side at this time; calculate the heat exchange q2 on the evaporator side according to the physical properties of the refrigerant, and Q = q1 = q2 = c p1 .q m .△t1=c p2 .q m .△t2 calculates the evaporator side outlet temperature t2'=t2+△t2; then calculates the average temperature of the evaporator side inlet temperature t2 and the evaporator side outlet temperature t2' as the actual qualitative temperature of the evaporator side The actual qualitative temperature t on the evaporator side 2p Query and obtain the refrigerant physical properties parameters on the evaporator side.

[0042] S45: Obtaining the countercurrent logarithmic mean temperature difference △t m, △t max The larger value is the difference between the inlet temperature of the condenser and the outlet temperature of the evaporator, and the difference between the outlet temperature of the condenser and the inlet temperature of the evaporator. min It is the smaller value of the difference between the inlet temperature of the condenser side and the outlet temperature of the evaporator side and the difference between the outlet temperature of the condenser side and the inlet temperature of the evaporator side.

[0043] S5: Based on heat transfer Q and counterflow logarithmic mean temperature difference △t m Estimate the heat transfer area A, select the pipe material and specifications, and calculate the pressure drop △P on the evaporator side i And shell side pressure drop △P L .

[0044] The calculation formula for estimating the heat transfer area A is: Where K is the primary heat transfer coefficient.

[0045] Calculate the evaporator side pressure drop △P i The steps include:

[0046] S511: Select the pipe material and specifications (outer diameter and wall thickness) on the evaporator side and calculate the required flow area on the evaporator side

[0047] Among them, d i is the inner diameter of the evaporator side tube, d i =d o -2×δ2,d o is the outer diameter of the evaporator side tube, δ2 is the wall thickness of the evaporator side tube;

[0048] S512: Calculate the refrigerant flow rate in the heat exchange tube shell

[0049] S513: Calculate the heat transfer area of ​​the structure A' = nπd o l; where n is the number of tubes, l is the estimated tube length, N p is the number of pipe passes.

[0050] S514: Calculate the Reynolds number on the evaporator side of the regenerative heat exchange tube Wherein, ρ2' is the refrigerant density on the evaporator side, and μ2' is the refrigerant dynamic viscosity on the evaporator side;

[0051] S515: Calculate the tube-side convection heat transfer coefficient h2, including:

[0052] judge Is it less than the set threshold m1? If not, then Yes, then

[0053] Wherein, λ2' is the thermal conductivity of the refrigerant on the evaporator side, and Pr2' is the Prandtl number of the refrigerant on the evaporator side;

[0054] S516: Calculate the evaporator side pressure drop △P i =△P L F t N p N t +△P n N t ; Among them, △P L is the pressure drop on the shell side; F t is the structural correction factor, N p is the number of tube passes, △P n is the pressure drop of the fluid flowing through the pipe inlet and outlet (Pa), N t is the number of shell passes in series.

[0055] Calculate the shell side pressure drop △P L The steps include:

[0056] S521: Select the pipe material and specifications (shell outer diameter and shell wall thickness) on the shell side and calculate the shell flow cross-sectional area D i is the shell inner diameter, d o is the outer diameter of the tube on the tube side;

[0057] S522: Calculate the Reynolds number on the shell side Where, μ1 is the dynamic viscosity of the refrigerant on the condenser side, q m is the refrigerant mass flow rate;

[0058] S523: Calculate the shell side heat transfer coefficient h1, including:

[0059] judge Is it less than the set threshold m1? If not, then Yes, then

[0060] Where λ1 is the thermal conductivity of the refrigerant on the condenser side, d e is the equivalent diameter of the shell side, d e =D S -d O , D S is the outer diameter of the shell, Pr1 is the Prandtl number of the refrigerant on the condenser side, and l is the estimated tube length;

[0061] S524: Calculate the shell side pressure drop Among them, λ o is the friction coefficient on the shell side, ρ1 is the refrigerant density on the condenser side, v1 is the refrigerant flow rate on the shell side,

[0062] In this embodiment, the threshold m1 is set to 60.

[0063] S6: Determine whether the pressure drop on the evaporator side and the pressure drop on the shell side meet the standard conditions. If the pressure drop on the evaporator side does not meet the standard conditions, reselect the tube material and specifications on the evaporator side. If the pressure drop on the shell side does not meet the standard conditions, reselect the tube material and specifications on the shell side. If the pressure drops on both sides meet the standard conditions, proceed to the next step.

[0064] Among them, the standard condition is that the pressure drop on the condenser side and the evaporator side of the heat exchange tube must meet the standard pressure drop value established by the carbon footprint energy efficiency value, that is, the shell side pressure drop ≤ JJ1, the evaporator side pressure drop ≤ JJ2, JJ1 and JJ2 are the pressure drop thresholds on the condenser side and evaporator side respectively.

[0065] In this embodiment, the pressure drop on the shell side needs to be ≤75 kPa, and the pressure drop on the evaporator side needs to be ≤25 kPa.

[0066] S7: Based on the heat transfer coefficient on the evaporator side and the heat transfer coefficient on the shell side, calculate the total heat transfer coefficient K' and the actual heat transfer area A of the heat exchange tube ” And the actual tube length l'; the calculation formula of the total heat transfer coefficient K' is:

[0067]

[0068] Actual heat transfer area A ” The calculation formula is:

[0069]

[0070] The calculation formula for the actual pipe length is:

[0071] Among them, h2 is the heat transfer coefficient of the tube, d o is the outer diameter of the evaporator side tube, d i is the inner diameter of the evaporator side tube, λ t is the thermal conductivity of the pipe, h1 is the shell heat transfer coefficient; Q is the heat transfer amount, △t m is the countercurrent logarithmic mean temperature difference.

[0072] S8: Determine the actual heat transfer area A ” Does the heat transfer area A' of the structure satisfy 1.05A"≤A'≤1.1A"? If yes, it proves that the above evaporator side structure and shell side structure are reasonably designed, and the subsequent steps are continued; if no, it jumps to step S5;

[0073] S9: Continue to optimize the internal thread of the heat recovery heat exchange tube to obtain the final optimized heat recovery heat exchange tube, including:

[0074] S91: Preliminary selection of the internal thread parameters of the heat recovery tube, including wing height e, helix angle α, number of wing Ns, and pitch p;

[0075] S92: Based on the heat transfer coefficient h'2 of the evaporator side after the heat exchange tube is optimized, and in combination with the heat transfer coefficient of the shell side, the optimized total heat transfer coefficient K" and the optimized heat transfer area A"' are calculated;

[0076]

[0077] Among them, d o is the outer diameter of the evaporator side tube, λ t The thermal conductivity of the pipe, h1 is the heat transfer coefficient on the shell side, Q is the heat transfer, △t m is the countercurrent logarithmic mean temperature difference;

[0078] The heat transfer coefficient h'2 of the evaporator side after the heat recovery heat exchange tube is optimized includes:

[0079] judge Is it less than the set threshold m1? If not, then yes, Where Re2 is the Reynolds number on the evaporator side, d i is the inner diameter of the tube on the evaporator side, λ2' is the thermal conductivity of the refrigerant on the evaporator side, and l is the estimated tube length;

[0080] S93: recalculate and obtain the optimized tube length l' based on the optimized heat transfer area, and determine whether the optimized tube length satisfies l'≤l' and l'=p×Ns. If yes, proceed to the next step; if no, readjust the internal thread parameters of the heat recovery heat exchange tube.

[0081] Among them, the calculation formula of the optimized tube length l" is:

[0082] When readjusting, the internal thread angle α is adjusted first, increasing by 1 degree each time until l” meets the requirement l”≤l', and then Ns and p are corrected, that is, l”=p×Ns until the design requirements are met;

[0083] S94: Calculate the optimized evaporator side friction coefficient f1 and the optimized shell side pressure drop △P' L And the optimized evaporator side pressure drop △P' i ;

[0084]

[0085] △P′ i =△P′ L F t N p N t +△Pn N t

[0086] Among them, Re2 is the Reynolds number on the evaporator side, Ns' is the number of wings after correction, λ o is the friction coefficient on the shell side, l” is the optimized tube length, d e is the shell side equivalent diameter, ρ1 is the refrigerant density on the condenser side, v1 is the refrigerant flow rate on the shell side, F t is the structural correction factor, N p is the number of tube passes, N t is the number of shell passes in series, △P n It is the pressure drop of the fluid flowing through the inlet and outlet of the pipeline.

[0087] S95: Determine whether the optimized shell-side pressure drop and the optimized evaporator-side pressure drop meet the standard conditions. If the optimized evaporator-side pressure drop or the optimized shell-side pressure drop does not meet the standard conditions, jump to step S91. If the pressure drops on both sides meet the standard conditions, the internal thread parameters of the heat recovery heat exchange tube at this time are used as the final optimization result to complete the final design of the heat recovery heat exchange tube.

[0088] The above-mentioned heat exchange carbon control design method based on the GWP value of the refrigerant is described below in conjunction with specific embodiments.

[0089] Example 1

[0090] Take the refrigerant type R404A (GWP is 3922) as an example.

[0091] 1. Calculation of carbon footprint energy efficiency value

[0092] Take the inlet temperature t1 of the condenser side as 40℃, the subcooling △t1 as 3℃, then the outlet temperature t1' of the shell side is 37℃, and the qualitative temperature of the condenser side is Calculate carbon footprint energy efficiency value The subcooling of the heat exchange tube needs to be adjusted. Taking the subcooling as 4°C, we get Then the subcooling of the heat exchange tube needs to be adjusted again, and the subcooling is set to 5℃, and we get The pre-set standard is met, so the supercooling is set to 5°C, and the other original data remain unchanged. Go to the next step of design.

[0093] 2. Raw data

[0094] Assuming the inlet temperature t1 of the condenser side (shell side) is 40°C and the subcooling △t1 is 5°C, the outlet temperature t1' of the shell side is 35°C.

[0095] In summary, we can get t1=40℃, △t1=5℃, t1'=35℃, and the qualitative temperature is The physical properties of the refrigerant fluid on the shell side are:

[0096] Specific heat of refrigerant on the condenser side c p1 =1683.9J / kg·K

[0097] Condenser side refrigerant dynamic viscosity μ1=0.000106p a ·s

[0098] Condenser side refrigerant thermal conductivity λ1=0.05767W / m·K

[0099] Condenser side refrigerant Prandtl number Pr1 = 3.11

[0100] Condenser side refrigerant density ρ1=979.1kg / m 3

[0101] Take the inlet temperature of the evaporator side (tube side) as 7°C. After the working conditions are determined, the refrigerant mass flow rate q in the heat exchanger can be calculated. m =0.295kg / s, assuming that t2=7℃ is taken as the qualitative temperature of the evaporator side, the assumed refrigerant physical properties of the evaporator side are:

[0102] Assumed specific heat of refrigerant on the evaporator side c p2 =1422.3J / kg·K

[0103] Assumed dynamic viscosity of refrigerant on the evaporator side μ2 = 0.0001645p a ·s

[0104] Assumed evaporator side refrigerant thermal conductivity λ2 = 0.07042 W / m·K

[0105] Assumed condenser side refrigerant Prandtl number Pr2 = 3.32

[0106] Assumed refrigerant density on the evaporator side ρ2 = 1122.9 kg / m 3

[0107] The heat transfer on the shell side can be calculated from the shell side data: q1 = c p1 .q m .△t1=2483.8W, from the heat transfer equation, it can be obtained that the heat transfer on the shell side is equal to the heat transfer on the evaporator side, that is, q1=q2=c p2 .q m .△t2=2483.8W, the outlet temperature of the evaporator side can be calculated as t2'=12.9℃, and △t2=5.9℃.

[0108] Pick is the qualitative temperature on the evaporator side, and the physical parameters of the refrigerant on the evaporator side are:

[0109] Specific heat of refrigerant on the evaporator side c p2 '=1437.5J / kg·K

[0110] Evaporator side refrigerant dynamic viscosity μ2'=0.000157p a ·s

[0111] Evaporator side refrigerant thermal conductivity λ2'=0.07W / m·K

[0112] Condenser side refrigerant Prandtl number Pr2'=3.3

[0113] Evaporator side refrigerant density ρ2'=1110.6kg / m 3 (Density on the evaporator side after correction)

[0114] From the above, we can get the countercurrent logarithmic mean temperature difference of this heat exchanger is △t m =27.55℃.

[0115] 3. Evaporator side calculation

[0116] (1) Query the data to estimate the heat transfer coefficient K = 2000W / ㎡·K, and estimate the heat transfer area of ​​the heat exchange tube

[0117] Select seamless copper tube Φ19×1, that is, the outer diameter of the pipe is do=0.019m, the wall thickness is δ2 is 0.001m, and the inner diameter is di=d o -2*δ2=0.017m

[0118] Required flow area on the tube side (evaporator side)

[0119] The refrigerant flow rate in the heat exchange tube is

[0120] Take the number of pipe passes N p =1, take the number of tubes per pass n = 1,

[0121] Estimated pipe length

[0122] Calculate the heat transfer area of ​​the structure

[0123] A'=nπd0l=1×3.14×0.019×0.76=0.0453㎡

[0124] Calculate the Reynolds number on the evaporator side of the regenerative heat exchange tube

[0125]

[0126] Calculate the tube side convection heat transfer coefficient h2

[0127] because When calculating the convective heat transfer coefficient on the evaporator side, the calculation formula needs to be multiplied by Make corrections, that is

[0128]

[0129] Calculation of pressure drop on evaporator side

[0130] The formula for calculating the pressure drop on the evaporator side is:

[0131] △P i =△P Li F t N p N t +△P n N t

[0132] In the formula, △P i is the pressure drop on the evaporator side (Pa); △P L F is the pressure drop caused by friction resistance when the fluid flows through a straight pipe (Pa); t For structural correction factors, take 1.5 for Φ19×1 pipe; N p is the number of tube passes; N t is the number of shell passes in series; △P n It is the pressure drop of the fluid flowing through the inlet and outlet of the pipeline (Pa).

[0133] Where △P L With △P n The calculation formula is

[0134]

[0135] In the formula, v2 is the refrigerant flow rate in the heat exchange tube shell in m / s; d i is the inner diameter of the tube; l is the estimated tube length; λ i is the friction coefficient, dimensionless, which can be obtained by looking up the graph; ρ2' is the density of the fluid in the tube kg / m 3 .

[0136] In summary, the pressure drop on the evaporator side is

[0137] Meets the requirements.

[0138] 4. Shell side calculation

[0139] (1) Shell inner diameter

[0140] The shell on the shell side is Φ25×2, so its inner diameter D i =0.021m

[0141] Determine the aspect ratio When calculating the heat transfer coefficient, multiply by Correct the shell side flow cross-sectional area

[0142] The shell flow cross-sectional area on the shell side is

[0143] (3) Shell side Reynolds number

[0144]

[0145] (4) Calculation of pressure drop on the shell side

[0146] Since there is no baffle and the fluid flows along the tube, the shell side pressure drop is directly calculated according to the tube pressure drop formula when the fluid flows through the straight tube part, but the tube inner diameter in its characteristic size should be the equivalent diameter d e , d e =D S -d O =0.021-0.019=0.002m, and the shell side velocity

[0147] The pressure drop on the shell side is

[0148] Meet the standard requirements;

[0149] (5) Calculation of heat transfer coefficient on the shell side

[0150]

[0151] 5. Calculation of heat transfer area required for heat exchange tubes

[0152] (1) Total heat transfer coefficient K' of the heat exchange tube

[0153]

[0154] (2) Calculation of actual heat transfer area

[0155] Therefore, it meets the requirements.

[0156] The actual tube length is

[0157] 6. Evaporator side optimization calculation

[0158] (1) Optimizing the internal thread;

[0159] (2) The inner tube is designed as a threaded type, and the Nusselt correlation is taken as

[0160]

[0161] Where e is the thread wing height m, d is the pipe inner diameter m, p is the pitch m, α is the helical angle, and Ns is the number of thread wings.

[0162] Known Right now (Refer to this formula to get the following formula)

[0163] The optimized heat transfer coefficient of the evaporator side can be obtained:

[0164]

[0165] Take e=0.0002m, α=5°, p=0.01m, Ns=25, is the correction factor, l' is the actual pipe length.

[0166] have to

[0167]

[0168] (3) Optimized overall heat transfer coefficient

[0169]

[0170] (4) Optimized heat transfer area

[0171] Meets the requirements.

[0172] Optimized tube length

[0173] Since p×Ns=0.01×25=0.25m≈0.243m, there is no need to correct Ns.

[0174] (5) Optimize the rear tube and shell resistance

[0175] Friction coefficient:

[0176] Meets standard requirements.

[0177] In accordance with the standard requirements, the design results of the heat recovery heat exchange tubes are output, and the calculation table is shown in Table 1.

[0178] Table 1 Design table of heat exchange tubes for refrigerant type R404A

[0179]

[0180]

[0181]

[0182]

[0183]

[0184] Example 2

[0185] Select the type of refrigerant and determine the GWP value of the refrigerant, taking R448A (GWP is 1387) as an example.

[0186] 1. Calculation of carbon footprint energy efficiency value

[0187] If the inlet temperature of the condenser side is 40℃ and the subcooling degree is 3℃, the outlet temperature of the shell side is 37℃. That is, t1=40℃, △t1=3℃, t1'=37℃, and the qualitative temperature of the condenser side is Calculate carbon footprint energy efficiency value Therefore, there is no need to adjust the subcooling of the heat exchange tube, that is, take the subcooling as 3℃, and keep the other original data unchanged. Go to the next step of design.

[0188] 2. Raw data

[0189] If the inlet temperature of the condenser side (shell side) is 40°C and the subcooling degree is 3°C, the outlet temperature of the shell side is 37°C.

[0190] In summary, we can get t1s = 40 °C, △t1 = 3 °C, t1' = 37 °C, and the qualitative temperature is At this time, the working pressure on the shell side is 1.81MPa.

[0191] The physical properties of the refrigerant fluid on the shell side are:

[0192] Specific heat of refrigerant on the condenser side c p1 =1676.8J / kg·K

[0193] Condenser side refrigerant dynamic viscosity μ1=0.0001157p a ·s

[0194] Condenser side refrigerant thermal conductivity λ1=0.075W / m·K

[0195] Condenser side refrigerant Prandtl number Pr1 = 2.6

[0196] Condenser side refrigerant density ρ1=1032.9kg / m 3

[0197] Take the inlet temperature of the evaporator side (tube side) as 7°C. After the working conditions are determined, the refrigerant mass flow rate q in the heat exchanger can be calculated. m =0.326kg / s, assuming t2=7℃ as the qualitative temperature, the refrigerant physical properties on the tube side are:

[0198] Assumed specific heat of refrigerant on the evaporator side c p2 =1452J / kg·K

[0199] Assumed dynamic viscosity of refrigerant on the evaporator side μ2 = 0.000173p a ·s

[0200] Assumed evaporator side refrigerant thermal conductivity λ2 = 0.09 W / m·K

[0201] Assumed condenser side refrigerant Prandtl number Pr2 = 2.8

[0202] Assumed refrigerant density on the evaporator side ρ2 = 1171.3 kg / m 3

[0203] The heat transfer on the shell side can be calculated from the shell side data: q1 = c p1 .q m .△t1=1640W, from the heat transfer equation, it can be obtained that the heat transfer on the shell side is equal to the heat transfer on the tube side, that is, q1=q2=c p2 .q m .△t2=1640W, it can be calculated that the outlet temperature on the tube side is t2'=10.5℃, and △t2=3.5℃.

[0204] Pick is the qualitative temperature, and the working pressure on the tube side is 0.82MPa. The physical parameters of the refrigerant on the tube side are:

[0205] Specific heat of refrigerant on the evaporator side c p2 '=1460J / kg·K

[0206] Dynamic viscosity of refrigerant on the evaporator side μ2'=0.00017p a ·s

[0207] Evaporator side refrigerant thermal conductivity λ2'=0.089W / m·K

[0208] Condenser side refrigerant Prandtl number Pr2'=2.78

[0209] Evaporator side refrigerant density ρ2'=1164.5kg / m 3

[0210] From the above, we can get the countercurrent logarithmic mean temperature difference of this heat exchanger is △t m =29.75℃.

[0211] 3. Calculation on the pipe side

[0212] (1) According to the data, the heat transfer coefficient K is estimated to be 2000W / ㎡·K, and the heat transfer area of ​​the heat exchange tube is estimated to be

[0213]

[0214] Select seamless copper tube Φ19×1, that is, the outer diameter of the pipe is do=0.019m, the wall thickness is δ2 is 0.001m, and the inner diameter is di=d o -2*δ2=0.017m

[0215] Required flow area on the tube side

[0216] The refrigerant flow rate in the heat exchange tube is

[0217] Take the number of pipe passes N p =1, the number of tubes per pass n = 1,

[0218] Estimated pipe length

[0219] Calculate the heat transfer area of ​​the tube

[0220] A'=nπd0l=1×3.14×0.019×0.47=0.028㎡

[0221] Calculate the Reynolds number on the evaporator side of the regenerative heat exchange tube

[0222]

[0223] Calculate the tube side convection heat transfer coefficient h2

[0224] because When calculating the convective heat transfer coefficient on the tube side, the calculation formula needs to be multiplied by Make corrections, that is

[0225]

[0226] Calculation of pressure drop on the tube side

[0227] The formula for calculating the pressure drop on the tube side is:

[0228] △P i =△P Li F t N p N t +△P n N t

[0229] In the formula, △P i is the pressure drop on the tube side (Pa); △P L F is the pressure drop caused by friction resistance when the fluid flows through a straight pipe (Pa);t For structural correction factors, take 1.5 for Φ19×1 pipe; N p is the number of tube passes; N t is the number of shell passes in series; △P n It is the pressure drop (Pa) of the fluid flowing through the inlet and outlet of the pipe box.

[0230] Where △P L With △P n The calculation formula is

[0231]

[0232] In the formula, v2 is the refrigerant flow rate in the heat exchange tube shell in m / s; d i is the inner diameter of the tube; l is the estimated tube length; λ i is the friction coefficient, dimensionless, which can be obtained by looking up the graph; ρ2' is the density of the fluid in the tube kg / m 3 .

[0233] In summary, the pressure drop on the tube side is

[0234] Meets the requirements.

[0235] 4. Shell side calculation

[0236] (1) Shell inner diameter

[0237] The shell on the shell side is Φ25×2, so its inner diameter D i =0.021m

[0238] Determine the aspect ratio When calculating the heat transfer coefficient, multiply by Correct the shell side flow cross-sectional area

[0239] The shell flow cross-sectional area on the shell side is

[0240] (3) Shell side Reynolds number

[0241]

[0242] (4) Calculation of pressure drop on the shell side

[0243] Since there is no baffle and the fluid flows along the tube, the shell side pressure drop is directly calculated according to the tube pressure drop formula when the fluid flows through the straight tube part, but the tube inner diameter in its characteristic size should be the equivalent diameter d e , d e =D S -d O =0.021-0.019=0.002m, and the shell side velocity

[0244] The pressure drop on the shell side is

[0245] Meet the standard requirements;

[0246] (5) Calculation of heat transfer coefficient on the shell side

[0247]

[0248] 5. Calculation of heat transfer area required for heat exchange tubes

[0249] (1) Total heat transfer coefficient of heat exchange tube

[0250]

[0251] (2) Actual heat transfer area

[0252] Therefore, it meets the requirements.

[0253] The actual tube length is

[0254] 6. Optimization calculation of pipe side

[0255] (1) Optimizing the internal thread;

[0256] (2) The inner tube is designed as a threaded type, and the Nusselt correlation is taken as

[0257]

[0258] Where e is the spiral wing height m, d is the inner diameter of the pipe m, p is the pitch m, α is the helical angle, and Ns is the number of spiral wings.

[0259] Known Right now

[0260] Available

[0261]

[0262] Take e=0.0002m, α=5°, p=0.01m, Ns=25,

[0263] have to

[0264]

[0265] (3) Optimized overall heat transfer coefficient

[0266]

[0267] (4) Optimized heat transfer area

[0268] Meets the requirements.

[0269] Optimized tube length

[0270] Correction: Since p×Ns=0.01×25=0.25m>0.17m, it is necessary to correct Ns, taking Ns′=17,

[0271] Then

[0272]

[0273]

[0274] Meets the requirements.

[0275] Meets the requirements, so no correction is required

[0276] (5) Optimize the rear tube and shell resistance

[0277] Friction coefficient:

[0278]

[0279] Meets standard requirements.

[0280] In accordance with the standard requirements, the design results of the heat recovery heat exchange tubes are output, and the calculation table is shown in Table 2 below.

[0281] Table 2 Design table of heat exchange tubes for refrigerant type R448A

[0282]

[0283]

[0284]

[0285]

[0286]

[0287] Of course, it is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, but also includes the same or similar structures that can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-limiting, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any reference numerals in the claims should not be regarded as limiting the claims involved.

[0288] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

[0289] The techniques, shapes, and structural parts not described in detail in the present invention are all well-known techniques.

Claims

1. A heat exchange carbon control design method based on the GWP value of refrigerant, characterized in that: include: S1: Select the type of refrigerant and determine the GWP of the refrigerant, where GWP is the global warming potential; S2: Calculate the carbon footprint energy efficiency value G based on the refrigerant; S3: Determine whether the carbon footprint value C and the refrigeration system energy efficiency value EER are compatible, that is, whether the carbon footprint energy efficiency value G meets the preset standard. If yes, proceed to the next step. Otherwise, adjust the subcooling degree of the heat exchange tube so that the carbon footprint energy efficiency value G meets the preset standard, and then proceed to the next step. S4: Based on the basic data on the condenser side and the evaporator side, determine the heat transfer capacity Q of the heat exchange tube and the logarithmic mean temperature difference △t of the countercurrent flow. m ; S5: Based on heat transfer Q and counterflow logarithmic mean temperature difference △t m Estimate the heat transfer area A, select the pipe materials and specifications on both sides, and calculate the pressure drop △P on the evaporator side i and condenser side pressure drop △P L ; S6: Determine whether the pressure drop on the evaporator side and the pressure drop on the condenser side meet the standard conditions. If the pressure drop on the evaporator side does not meet the standard conditions, reselect the pipe material and specifications on the evaporator side. If the pressure drop on the condenser side does not meet the standard conditions, reselect the pipe material and specifications on the condenser side. If the pressure drops on both sides meet the standard conditions, proceed to the next step. S7: Calculate the actual heat transfer area A based on the heat transfer coefficient on the evaporator side and the heat transfer coefficient on the condenser side ” and the actual tube length l', determine the actual heat transfer area A ” Does the heat transfer area A' satisfy k1·A"≤A'≤k2·A"? If yes, it proves that the above evaporator side structure and condenser side structure are reasonably designed, and the design result of the heat recovery heat exchange tube is obtained; if no, it jumps to step S5, where 0.9 <k1<k2<1.5。 2. A heat exchange carbon control design method based on the GWP value of refrigerant according to claim 1, characterized in that: In step S3, the pre-set standard is as follows: If the GWP value range is 0-150, the standard range of the carbon footprint energy efficiency value G is ≤10kg·a; If the GWP value is 150-1500, the standard range of the carbon footprint energy efficiency value G is ≤90kg·a; If the GWP value is >1500, the standard range of the carbon footprint energy efficiency value G is ≤245kg·a.

3. A heat exchange carbon control design method based on the refrigerant GWP value according to claim 1, characterized in that: In step S2, the carbon footprint energy efficiency value G is calculated as follows: Among them, C is the carbon footprint value, EER is the energy efficiency value of the refrigeration system, Q L is the amount of refrigerant, S is the refrigerant leakage rate, GWP is the global warming potential of the refrigerant, a is the operating years, and COP is the refrigeration coefficient.

4. A heat exchange carbon control design method based on the refrigerant GWP value according to claim 1, characterized in that: In step S4, the basic data on the condenser side includes the condenser side inlet temperature t1, the subcooling degree Δt1, and the condenser side outlet temperature t1'; wherein t1'=t1-Δt1; the basic data on the evaporator side includes the evaporator side inlet temperature t2, the evaporator side outlet temperature t2', and the superheat degree Δt2; Based on the basic data of the condenser side and the evaporator side, determine the heat transfer Q of the heat exchange tube and the countercurrent logarithmic mean temperature difference △t m ,include: S41: Calculate the qualitative temperature of the condenser side, the qualitative temperature of the condenser side t 1p The calculation formula is: S42: determining the physical parameters of the refrigerant fluid based on the qualitative temperature on the condenser side; the physical parameters of the refrigerant fluid include the refrigerant specific heat on the condenser side and the evaporator side, the refrigerant dynamic viscosity on the condenser side and the evaporator side, the refrigerant thermal conductivity on the condenser side and the evaporator side, the refrigerant Prandtl number on the condenser side and the evaporator side, and the refrigerant density on the condenser side and the evaporator side; S43: Determine the heat exchange amount Q based on the physical parameters of the refrigerant fluid. The heat exchange amount Q is calculated as follows: Q=q1=q2=c p1 .q m .△t1 Among them, q1 is the heat exchange on the condenser side, q2 is the heat exchange on the evaporator side, c p1 is the specific heat of the refrigerant on the condenser side, q m is the refrigerant mass flow rate; S44: Obtain superheat △t2 and evaporator outlet temperature t2' based on heat exchange Q. The calculation formula of △t2 is: Among them, c p2 is the refrigerant specific heat on the evaporator side; the outlet temperature on the evaporator side t2'=t2+△t2; S45: Obtaining the countercurrent logarithmic mean temperature difference △t m , △t max The larger value is the difference between the inlet temperature of the condenser and the outlet temperature of the evaporator, and the difference between the outlet temperature of the condenser and the inlet temperature of the evaporator. min It is the smaller value of the difference between the inlet temperature of the condenser side and the outlet temperature of the evaporator side and the difference between the outlet temperature of the condenser side and the inlet temperature of the evaporator side.

5. A heat exchange carbon control design method based on the refrigerant GWP value according to claim 1, characterized in that: In step S5, the calculation formula for estimating the heat transfer area A is: Where K is the primary heat transfer coefficient.

6. A heat exchange carbon control design method based on the refrigerant GWP value according to claim 1, characterized in that: In step S5, the evaporator side pressure drop ΔP is calculated i The steps include: S511: Select the pipe material and specifications on the evaporator side and calculate the required flow area on the evaporator side Among them, d i is the inner diameter of the evaporator side tube, d i =d o -2×δ2,d o is the outer diameter of the evaporator side tube, δ2 is the wall thickness of the evaporator side tube, and the tube material and specification on the evaporator side refer to the outer diameter and wall thickness of the evaporator side; S512: Calculate the refrigerant flow rate in the heat exchange tube shell Where ρ2' is the refrigerant density on the evaporator side, q m is the refrigerant mass flow rate; S513: Calculate the heat transfer area of ​​the structure A' = nπd o l; where n is the number of tubes, l is the estimated tube length, N p is the number of pipe passes; S514: Calculate the Reynolds number on the evaporator side of the regenerative heat exchange tube Wherein, μ2' is the dynamic viscosity of the refrigerant on the evaporator side; S515: Calculate the evaporator side convection heat transfer coefficient h2, including: judge Is it less than the set threshold m1? If not, then Yes, then Wherein, λ2' is the thermal conductivity of the refrigerant on the evaporator side, and Pr2' is the Prandtl number of the refrigerant on the evaporator side; S516: Calculate the evaporator side pressure drop △P i =△P L F t N p N t +△P n N t ; Among them, △P L is the pressure drop on the condenser side; F t is the structural correction factor, N p is the number of tube passes, △P n is the pressure drop of the fluid flowing through the pipe inlet and outlet (Pa), N t is the number of shell passes in series.

7. A heat exchange carbon control design method based on the refrigerant GWP value according to claim 1 or 6, characterized in that: In step S5, the pressure drop ΔP on the condenser side is calculated. L The steps include: S521: Select the pipe material and specifications on the condenser side and calculate the shell flow cross-sectional area D i is the shell inner diameter, d o is the outer diameter of the tube on the tube side; S522: Calculate the Reynolds number on the condenser side Where, μ1 is the dynamic viscosity of the refrigerant on the condenser side, q m is the refrigerant mass flow rate; S523: Calculate the heat transfer coefficient h1 on the condenser side, including: judge Is it less than the set threshold m1? If not, then Yes, then Where λ1 is the thermal conductivity of the refrigerant on the condenser side, d e is the equivalent diameter of the condenser side, d e =D S -d O , D S is the outer diameter of the shell, Pr1 is the Prandtl number of the refrigerant on the condenser side, and l is the estimated tube length; S524: Calculate the pressure drop on the condenser side Among them, λ o is the friction coefficient on the condenser side, ρ1 is the refrigerant density on the condenser side, v1 is the refrigerant flow rate on the condenser side, 8. A heat exchange carbon control design method based on the refrigerant GWP value according to claim 1, characterized in that: The standard condition is that the pressure drop on the condenser side and the evaporator side of the heat exchange tube must meet the standard pressure drop value established by the carbon footprint energy efficiency value G, that is, the pressure drop on the condenser side ≤ JJ1, and the pressure drop on the evaporator side ≤ JJ2, where JJ1 and JJ2 are the pressure drop thresholds on the condenser side and the evaporator side respectively.

9. A heat exchange carbon control design method based on the refrigerant GWP value according to claim 1, characterized in that: Actual heat transfer area A ” The calculation formula is: The calculation formula of the actual pipe length l' is: Where K' is the total heat transfer coefficient, h2 is the heat transfer coefficient on the evaporator side, and d o is the outer diameter of the evaporator side tube, d i is the inner diameter of the evaporator side tube, λ t is the thermal conductivity of the pipe, h1 is the heat transfer coefficient on the condenser side; Q is the heat transfer amount, △t m is the countercurrent logarithmic mean temperature difference, n is the number of tubes, N p is the number of pipe passes.

10. A heat regeneration heat exchange tube device, applicable to the heat exchange carbon control design method based on the refrigerant GWP value according to claims 1-9, characterized in that: include: A heat recovery heat exchange tube, wherein a sleeve is arranged inside the heat recovery heat exchange tube, and the sleeve adopts an internal thread structure; an evaporator interface tube is arranged on one side of the heat recovery heat exchange tube, and the evaporator interface tube is a pipe without an elbow, connected to the evaporator inlet; a condenser interface tube is arranged on the other side of the heat recovery heat exchange tube, and the condenser interface tube is a pipe with an elbow, connected to the condenser outlet; on the heat recovery heat exchange tube, a throttle valve interface is arranged between the condenser interface tube and the evaporator interface tube, which is used to connect to the throttle valve so that the refrigerant from the condenser flows to the throttle valve.

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