CN105136342A - System and method for improving measurement precision of heat exchange amount of heat exchanger under temperature differential condition - Google Patents
System and method for improving measurement precision of heat exchange amount of heat exchanger under temperature differential condition Download PDFInfo
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Abstract
The invention discloses a system and method for improving the measurement precision of the heat exchange amount of a heat exchanger under a temperature differential condition. The inlet and the outlet of a secondary-side fluid circulation device are connected through a connecting pipeline; a flow controller is arranged between the inlet of the secondary-side fluid circulation device and the first inlet of a tested heat exchanger; a first temperature sensor is arranged between the outlet of the flow controller and the first inlet of the tested heat exchanger; a second temperature sensor is arranged between the outlet of the secondary-side fluid circulation device and the first inlet of the tested heat exchanger; a first flowmeter is designed at the first inlet or first outlet of the tested heat exchanger; a primary-side fluid supply device is connected with the secondary-side fluid circulation device; the outlet of the primary-side fluid supply device is provided with a third temperature sensor; and a second flowmeter is designed at the inlet or outlet of the primary-side fluid supply device. According to the system and method of the invention, a heat balance test principle is adopted; the primary-side fluid supply device is additionally adopted, so that the heat exchange amount of the tested heat exchanger can be obtained indirectly; and therefore, the test precision of the heat exchange amount of the tested heat exchanger can be obviously improved.
Description
Technical field
The present invention relates to heat interchanger measuring technology, under specifically belonging to a kind of micro-temperature difference condition, measure the system and method for heat interchanger heat exchange amount.
Background technology
In heat exchanger industry, in order to detect the performance of heat interchanger, usually need employing performance testing device of heat exchanger, the test philosophy of this device is enthalpy potential method substantially, namely by measuring the mass rate of a side liquid and importing and exporting the heat exchange amount that enthalpy difference calculates this heat interchanger.When fluid is monophasic fluid, such as water, just can calculate the enthalpy of water by the out temperature measuring water.Although this measuring method is simply easy to realize, but but there is certain shortcoming, the measuring accuracy of i.e. heat exchange amount is larger by the impact of fluid inlet and outlet enthalpy difference or the temperature difference, when the import and export enthalpy difference of fluid or the temperature difference less, the measuring error of the method is larger, is that water is illustrated as an example below with fluid.
Assuming that the uncertainty of measurement of mass rate is 0.1% (k=3), the measuring accuracy of temperature is 0.1 DEG C (k=2), ignores the impact of leaking heat.
Condition 1: assuming that the mass rate of water is 1kg/s, inlet temperature during inflow heat exchanger is 20 DEG C, outlet temperature when flowing out from heat interchanger is 30 DEG C, and the specific heat at constant pressure of 25 DEG C of water is 4.1816kJ/kg DEG C, then heat exchange amount is Q=1 × (30-20) × 4.1816=41.816kW.The uncertainty of measurement of condition 1 is 0.592kW (k=2), see table one, and calculating reference " use evaluation of uncertainty in measurement " of uncertainty of measurement, the 3rd edition, 246 pages, China Measuring Press, 2009 years.
Condition 2: assuming that the mass rate of water is 10kg/s, inlet temperature during inflow heat exchanger is 20 DEG C, outlet temperature when flowing out from heat interchanger is 21 DEG C, and the specific heat at constant pressure of 20.5 DEG C of water is 4.1840kJ/kg DEG C, then heat exchange amount is Q=10 × (21-20) × 4.1840=41.840kW.The uncertainty of measurement of condition 2 is 5.91kW (k=2), see table two.
As can be seen from above two kinds of situations, although heat exchange amount is identical under two kinds of conditions, the measuring accuracy of heat exchange amount but differs widely.When the fluid inlet and outlet temperature difference small (being less than or equal to 5 DEG C), the measuring accuracy how improving heat exchange amount is the important subject in industry always.Wherein, the most frequently used method adopts more high-precision temperature sensor exactly, such as the measuring accuracy of temperature sensor is brought up to 0.01 DEG C (k=2), if adopt this temperature sensor in condition 2, so the uncertainty of measurement of condition 2 is just 0.592kW (K=2), as table three.
But above-mentioned result of calculation is theoretical precision, in engineering practice, also there is following problem:
1) more high price is more expensive for sensor price comparison costliness, and precision, and should not measure at the scene, and this directly affects the popularization of test method;
2) in test process, inevitably there is the leakage heat of sensor, and the problem of fluid temperature (F.T.) field uniformity, even if employing measuring accuracy is the temperature sensor of 0.01 DEG C, the temperature uncertainty of actual measurement also can higher than the temperature uncertainty in aforementioned theory calculate, therefore leak heat and the impact of temperature homogeneity to reduce, it is very high that the whole test macro for heat interchanger builds difficulty;
3) when the import and export temperature difference of fluid reduces further, if the temperature difference is at 0.1 DEG C ~ 1 DEG C, at present also again without better solution.
Summary of the invention
The technical problem to be solved in the present invention measures the system and method for heat interchanger heat exchange amount under being to provide a kind of micro-temperature difference condition, the heat exchange that can improve heat interchanger when the heat exchanger inlet and outlet temperature difference is small measures accuracy of measurement.
For solving the problems of the technologies described above, under micro-temperature difference condition provided by the invention, measuring the system of heat interchanger heat exchange amount, comprising tested heat interchanger, secondary side fluid circulating device and primary side fluid supply apparatus;
Described tested heat interchanger comprises the first entrance, the first outlet, the second entrance and the second outlet, and wherein the first entrance is connected with described secondary side fluid circulating device with the first outlet, and the second entrance and the second outlet are flowed into by another heat exchanging fluid and flow out;
Described secondary side fluid circulating device has flow controller, entrance A and outlet B, wherein entrance A is connected by a connecting line with outlet B, described flow controller makes the fluid flow constant of inflow tested heat interchanger first entrance, first entrance of described tested heat interchanger is provided with one first temperature sensor, be provided with one second temperature sensor between first outlet of tested heat interchanger, a first-class gauge is located at the first entrance of tested heat interchanger or the first outlet of tested heat interchanger;
Described primary side fluid supply apparatus is communicated with secondary side fluid circulating device, and exit is provided with a three-temperature sensor, one second gauge is located at porch or the exit of primary side fluid supply apparatus, described primary side fluid supply apparatus provides the fluid of steady temperature and flow, and the fluid flow provided by changing primary side fluid supply apparatus makes the fluid temperature (F.T.) of inflow tested heat interchanger first entrance constant.
In said structure, described entrance A is near the first entrance of tested heat interchanger, outlet B is near the first outlet of tested heat interchanger, described flow controller is located between the first entrance of tested heat interchanger and entrance A, described first temperature sensor is located between the outlet of flow controller and the first entrance of tested heat interchanger, and the second temperature sensor is located between the first outlet of tested heat interchanger and outlet B.Or, described entrance A is near the first entrance of tested heat interchanger, outlet B is near the first outlet of tested heat interchanger, described flow controller is located between the first outlet of tested heat interchanger and outlet B, described first temperature sensor is located between the first entrance of tested heat interchanger and entrance A, second temperature sensor is located between the entrance of flow controller and first of tested heat interchanger export, and the porch of described primary side fluid supply apparatus is provided with one the 4th temperature sensor.
In said structure, described primary side fluid supply apparatus is directly communicated with secondary side fluid circulating device, wherein the outlet of primary side fluid supply apparatus is connected with the entrance A of secondary side fluid circulating device, the entrance of primary side fluid supply apparatus is connected with the outlet B of secondary side fluid circulating device, the fluid part flowed out from the outlet B of secondary side fluid circulating device flows into primary side fluid supply apparatus, flowed into the first entrance of tested heat interchanger by flow controller after another part flows back to the fluid chemical field that the entrance A of secondary side fluid circulating device and primary side fluid supply apparatus provide, and it is identical with the fluid flow flowing into primary side fluid supply apparatus from secondary side fluid circulating device from the fluid flow of primary side fluid supply apparatus inflow secondary side fluid circulating device, or, described primary side fluid supply apparatus is directly communicated with secondary side fluid circulating device, wherein the outlet of primary side fluid supply apparatus is connected with the outlet B of secondary side fluid circulating device, the entrance of primary side fluid supply apparatus is connected with the entrance A of secondary side fluid circulating device, the fluid chemical field rear portion that the fluid flowed out from the outlet B of secondary side fluid circulating device and primary side fluid supply apparatus provide flows back to primary side fluid supply apparatus, another part is flowed into the entrance A of secondary side fluid circulating device and is flowed into the first entrance of tested heat interchanger by flow controller, and the fluid flow flowing back to primary side fluid supply apparatus is identical with the fluid flow that primary side fluid supply apparatus provides.
Or in said structure, described primary side fluid supply apparatus is connected with secondary side fluid circulating device by an Intermediate Heat Exchanger, wherein the outlet of primary side fluid supply apparatus is communicated with the first entrance of Intermediate Heat Exchanger, the entrance of primary side fluid supply apparatus and the first outlet of Intermediate Heat Exchanger, the outlet B of secondary side fluid circulating device is communicated with the second entrance of Intermediate Heat Exchanger, the entrance A of secondary side fluid circulating device and the second outlet of Intermediate Heat Exchanger, the porch of described primary side fluid supply apparatus is provided with one the 4th temperature sensor.
Further, between the outlet of described flow controller and the first entrance of tested heat interchanger, be provided with one first pressure transducer, between the outlet of secondary side fluid circulating device and first of tested heat interchanger exports, be provided with one second pressure transducer.
Further, the porch of described primary side fluid supply apparatus is provided with one the 4th temperature sensor.
Wherein, described flow controller is water pump or water pump and variable valve.
Wherein, described primary side fluid supply apparatus comprises pump, flowrate control valve, heating refrigeratory.
The present invention improves the method that heat interchanger heat exchange measures the system realization of accuracy of measurement under also providing and adopting above-mentioned micro-temperature difference condition, wherein:
First temperature sensor monitors of secondary side fluid circulating device flows into the fluid temperature (F.T.) of tested heat interchanger first entrance, second temperature sensor monitors exports the fluid temperature (F.T.) flowed out from tested heat interchanger first, first-class gauge monitoring stream enters tested heat interchanger first entrance or exports the fluid flow flowed out from tested heat interchanger first; The three-temperature sensor of primary side fluid supply apparatus monitors the fluid temperature (F.T.) flowed out from primary side fluid supply apparatus, the fluid flow that the monitoring of second gauge flows into primary side fluid supply apparatus or flows out from primary side fluid supply apparatus;
The fluid temperature (F.T.) flowing into tested heat interchanger first entrance remains at same probe temperature, the fluid flow that the flow controller of secondary side fluid circulating device controls to flow into tested heat interchanger first entrance remains on same test traffic, and the fluid temperature (F.T.) that primary side fluid supply apparatus provides remains on same supplying temperature;
Heat-insulation and heat-preservation (temperature that controls environment makes it close to the fluid temperature (F.T.) in tested heat interchanger, and makes leakage heat be less than 1% of tested heat interchanger heat exchange amount) is carried out to whole system, when system stable operation is in thermal equilibrium state, so
Q＝F1*C1*(T2-T1)＝F2*C2*(T2-T3)-W+Q
leak+q≈F2*C2*(T2-T3)-W+q
W＝(M*H1*S)/(367.7*E)
q＝(M*H2*S)/367.7
Wherein, Q is the heat exchange amount of tested heat interchanger, F1 is the mass rate of the fluid that tested heat interchanger first entrance flows into, C1 is the mean specific heat of the fluid that tested heat interchanger first entrance flows into, T1 is the temperature of the fluid that tested heat interchanger first entrance flows into, T2 is the temperature of the fluid that the outlet of tested heat interchanger first is flowed out, the mass rate of the fluid that F2 provides for primary side fluid supply apparatus, C2 is the mean specific heat of the fluid that primary side fluid supply apparatus flows out, T3 is the temperature of the fluid that primary side fluid supply apparatus flows out, W is the power of the flow controller in secondary side fluid circulating device, Q
leakfor pipeline leaks heat, q is the heat energy that heat interchanger inner fluid transforms because of friction, and M is the volumetric flow rate of the fluid that tested heat interchanger first entrance flows into, and H1 is lift, S is the specific density of the fluid that tested heat interchanger first entrance flows into, E is the efficiency of pump in flow controller, H2 is the design resistance of tested heat interchanger.
In the above-mentioned methods, when primary side fluid supply apparatus is directly communicated with secondary side fluid circulating device, the outlet of primary side fluid supply apparatus is connected with the entrance A of secondary side fluid circulating device, the entrance of primary side fluid supply apparatus is connected with the outlet B of secondary side fluid circulating device, the fluid part flowed out from the outlet B of secondary side fluid circulating device flows into primary side fluid supply apparatus, another part flows back to the entrance A of secondary side fluid circulating device, the fluid flow flowing into primary side fluid supply apparatus is identical with the fluid flow flowed out from primary side fluid supply apparatus, control fluid that primary side fluid supply apparatus provides and export the fluid temperature (F.T.) that blending ratio that B flows back to the fluid of secondary side fluid circulating device entrance A makes tested heat interchanger first entrance flow into from secondary side fluid circulating device and remain at same probe temperature,
When primary side fluid supply apparatus is connected with secondary side fluid circulating device by an Intermediate Heat Exchanger, the outlet of primary side fluid supply apparatus is communicated with the first entrance of Intermediate Heat Exchanger, the entrance of primary side fluid supply apparatus and the first outlet of Intermediate Heat Exchanger, the outlet of secondary side fluid circulating device is communicated with the second entrance of Intermediate Heat Exchanger, the entrance of secondary side fluid circulating device and the second outlet of Intermediate Heat Exchanger.
Preferably, the 4th temperature sensor monitors flows into the fluid temperature (F.T.) of primary side fluid supply apparatus from secondary side fluid circulating device, so
Q＝F1*C1*(T2-T1)＝F2*C2*(T4-T3)-W+Q
leak+q
Wherein, T4 is the temperature of the fluid that primary side fluid supply apparatus flows into.
In the above-mentioned methods, tested heat interchanger is carried out insulation (leak heat and be less than 1% of tested heat interchanger heat exchange amount), and make without heat exchanging fluid between the second entrance of tested heat interchanger and the second outlet, when system stable operation,
Q＝q
W-Q
leak≈W＝F2*C2*(T2-T3)
The uncertainty of measurement of the power of pump in flow controller in secondary side fluid circulating device is calculated, wherein T2=q/F1/C1+T1 according to the value of F2, T2, T3, standard uncertainty, probability distribution, sensitivity coefficient and partial uncertainty;
The uncertainty of measurement of the heat energy that tested heat interchanger inner fluid transforms because of friction is calculated according to the value of F1, H2, standard uncertainty, probability distribution, sensitivity coefficient and partial uncertainty;
According to F2, T1, T2, W-Q
leak, the value of q, standard uncertainty, probability distribution, sensitivity coefficient, partial uncertainty calculate the uncertainty of measurement of the heat exchange amount of tested heat interchanger.
Preferably, described flow controller is water pump, is measured the shaft power of water pump by the torque rotational speed meter be arranged in water pump input shaft.
The present invention has set up primary side fluid supply apparatus, adopt thermally equilibrated test philosophy, each fluid temperature (F.T.) flowing into tested heat interchanger in test process is made to remain on same probe temperature by the fluid flow and temperature controlling primary side fluid supply apparatus, although the import and export temperature difference of tested like this heat interchanger is small, but when test macro is in stable operation, the heat exchange amount of tested heat interchanger can be obtained by the heat exchange amount of primary side fluid supply apparatus indirectly, and what therefore can significantly improve tested heat interchanger changes heat amount test precision.
Accompanying drawing explanation
Fig. 1 is the structural representation of the first embodiment of the present invention;
Fig. 2 is the structural representation of the second embodiment of the present invention;
Fig. 3 is the composition schematic diagram of primary side fluid supply apparatus in the present invention.
Wherein description of reference numerals is as follows:
1 is tested heat interchanger; 2 is primary side fluid supply apparatus; 21 is pump; 22 is flowrate control valve; 23 is electric heater; 24 is cooling unit; 3 is Intermediate Heat Exchanger.
Embodiment
Below in conjunction with accompanying drawing and embodiment, the present invention is further detailed explanation.
Measure the first embodiment of the system of heat interchanger heat exchange amount under micro-temperature difference condition provided by the invention, as shown in Figure 1, comprise tested heat interchanger 1, secondary side fluid circulating device and primary side fluid supply apparatus 2;
Described tested heat interchanger 1 comprises the first entrance, the first outlet, the second entrance and the second outlet, and wherein the first entrance is connected with described secondary side fluid circulating device with the first outlet, and the second entrance and the second outlet then flow into for a heat exchanging fluid and flow out;
The entrance A of described secondary side fluid circulating device is connected by a connecting line with outlet B, and be provided with a flow controller between this entrance A and the first entrance of tested heat interchanger 1, one first temperature sensor and one first pressure transducer is provided with between the outlet of described flow controller and the first entrance of tested heat interchanger 1, one second temperature sensor and one second pressure transducer is provided with between the outlet B of secondary side fluid circulating device and first of tested heat interchanger 1 exports, one first-class gauge to be located between the outlet of flow controller and the first entrance of tested heat interchanger 1 or first of tested heat interchanger 1 to be exported between the outlet B of secondary side fluid circulating device, for test tested heat interchanger 1 first entrance and first export between fluid flow, in the present embodiment, before first-class gauge is located at the first entrance of tested heat interchanger 1,
Described primary side fluid supply apparatus 2 is directly communicated with secondary side fluid circulating device, wherein the outlet of primary side fluid supply apparatus 2 is connected with the entrance of secondary side fluid circulating device, the entrance of primary side fluid supply apparatus is connected with the outlet of secondary side fluid circulating device, the exit of primary side fluid supply apparatus 2 is provided with a three-temperature sensor and a second gauge, and the porch of primary side fluid supply apparatus 2 is provided with one the 4th temperature sensor.
Wherein, the fluid part flowed out from secondary side fluid circulating device outlet B flows into primary side fluid supply apparatus 2, flowed into the first entrance of tested heat interchanger 1 by flow controller after another part flows back to the fluid chemical field that secondary side fluid circulating device entrance A and primary side fluid supply apparatus 2 provide, and the fluid flow that primary side fluid supply apparatus 2 provides is identical with the fluid flow flowing into primary side fluid supply apparatus 2 from secondary side fluid circulating device, therefore second gauge also can be located at the porch of primary side fluid supply apparatus 2.
Simultaneously, when not considering that leakage heat and flowage friction affect, the fluid temperature (F.T.) flowing into primary side fluid supply apparatus 2 from the outlet B of secondary side fluid circulating device, with to export from first of tested heat interchanger 1 fluid temperature (F.T.) flowed out basically identical, therefore can omit the 4th temperature sensor.
In the present embodiment, flow controller is pump, can be controlled the fluid flow of tested heat interchanger 1 by the rotating speed (or frequency) changing pump.
In said system, first temperature sensor monitors of secondary side fluid circulating device flows into the fluid temperature (F.T.) of tested heat interchanger first entrance, second temperature sensor monitors exports the fluid temperature (F.T.) flowed out from tested heat interchanger first, first-class gauge monitoring stream enters tested heat interchanger first entrance or exports the fluid flow flowed out from tested heat interchanger first; The three-temperature sensor of primary side fluid supply apparatus 2 monitors the fluid temperature (F.T.) flowed out from primary side fluid supply apparatus 2,4th temperature sensor monitors flows into the fluid temperature (F.T.) T4 of primary side fluid supply apparatus 2 from secondary side fluid circulating device, the fluid flow that the monitoring of second gauge flows into primary side fluid supply apparatus or flows out from primary side fluid supply apparatus.
When the fluid that secondary side fluid circulating device provides is heated in tested heat interchanger 1, the fluid temperature (F.T.) that A point provides must lower than the fluid temperature (F.T.) of tested heat interchanger 1 first entrance; When fluid is cooled in tested heat interchanger 1, the water temperature that A point provides must higher than the fluid temperature (F.T.) of tested heat interchanger 1 first entrance.
The fluid part flowed out from secondary side fluid circulating device outlet B flows into primary side fluid supply apparatus 2, another part flows back to secondary side fluid circulating device entrance A and flows into tested heat interchanger 1 again after the fluid chemical field that primary side fluid supply apparatus 2 flows out, the fluid temperature (F.T.) flowed out from primary side fluid supply apparatus 2 remains on same supplying temperature, and the fluid flow flowing into primary side fluid supply apparatus 2 is identical with the fluid flow flowed out from primary side fluid supply apparatus 2; Control fluid that primary side fluid supply apparatus 2 provides and export the fluid temperature (F.T.) that blending ratio that B flows back to the fluid of secondary side fluid circulating device entrance A makes tested heat interchanger 1 first entrance flow into from secondary side fluid circulating device and remain at same probe temperature;
Heat-insulation and heat-preservation is carried out to whole system, when system stable operation is in thermal equilibrium state, so
Q＝F1*C1*(T2-T1)＝F2*C2*(T4-T3)-W+Q
leak+q≈F2*C2*(T2-T3)-W+Q
leak+q≈F2*C2*(T2-T3)-W+q
W＝(M*H1*S)/(367.7*E)
q＝(M*H2*S)/367.7
Wherein, Q is the heat exchange amount of tested heat interchanger, F1 is the mass rate of the fluid that tested heat interchanger first entrance flows into, C1 is the mean specific heat of the fluid that tested heat interchanger first entrance flows into, T1 is the temperature of the fluid that tested heat interchanger first entrance flows into, T2 is the temperature of the fluid that the outlet of tested heat interchanger first is flowed out, the mass rate of the fluid that F2 provides for primary side fluid supply apparatus, C2 is the mean specific heat of the fluid that primary side fluid supply apparatus flows out, T3 is the temperature of the fluid that primary side fluid supply apparatus flows out, W is the power of the flow controller in secondary side fluid circulating device, Q
leakfor pipeline leaks heat, q is the heat energy that heat interchanger inner fluid transforms because of friction, and M is the volumetric flow rate of the fluid that tested heat interchanger first entrance flows into, and H1 is lift, S is the specific density of the fluid that tested heat interchanger first entrance flows into, E is the efficiency of pump in flow controller, H2 is the design resistance of tested heat interchanger.
Tested heat interchanger is carried out insulation, and makes, without heat exchanging fluid between the second entrance of tested heat interchanger and the second outlet, during system stable operation, can be similar to and think and then can record W-Q by Q=q
leak≈ W=F2*C2* (T2-T3), the uncertainty of measurement of the power of pump in flow controller in secondary side fluid circulating device is calculated, wherein T2=q/F1/C1+T1 according to the value of F2, T2, T3, standard uncertainty, probability distribution, sensitivity coefficient and partial uncertainty;
The uncertainty of measurement of the heat energy that tested heat interchanger inner fluid transforms because of friction is calculated according to the value of F1, H2, standard uncertainty, probability distribution, sensitivity coefficient and partial uncertainty;
According to F2, T1, T2, W-Q
leak, the value of q, standard uncertainty, probability distribution, sensitivity coefficient, partial uncertainty calculate the uncertainty of measurement of the heat exchange amount of tested heat interchanger.
Below, again for condition 2, analyze, wherein suppose that the mass rate of water is 10kg/s, inlet temperature during inflow heat exchanger is 20 DEG C, outlet temperature when flowing out from heat interchanger is 21 DEG C, and the specific heat at constant pressure of 20.5 DEG C of water is 4.1840kJ/kg DEG C, then heat exchange amount is Q=10 × (21-20) × 4.1840=41.840kW.
First, by provision for thermal insulation Qleak is reduced to and can ignores (such as: package unit is placed in the environment of 20 DEG C).
Pump convection cell work is W=(M*H*S)/(367.7*E), and wherein, W is shaft power kW, M is volumetric flow rate m
3/ h, H are lift m, S is specific density (water20 DEG C=1.0), and E is pump efficiency.The heat energy that pipeline inner fluid should rub and transform is q=(M*H*S)/(367.7) kW.
The design resistance of heat interchanger is generally less than 5 meters, and the resistance of ducting is generally also less than 5 meters.The efficiency of a centrifugal pump is generally higher than 50%.Thus, condition 2 times, the shaft power W of pump is:
(10*3600/998.06)*10*0.998/(367.7*0.5)＝1.958kW。
By measuring heat exchanger inlet and outlet pressure reduction, can estimate fluid and flow through heat interchanger, the change of internal energy q caused due to heat of friction is:
(10*3600/998.06)*5*0.998/(367.7)＝0.490kW。
The uncertainty of measurement that can be obtained q by table four is 0.0979kW (K=2).
Shaft power due to pump is an estimated value, therefore first needs to measure it.For this reason, first tested heat interchanger 1 is carried out insulation, and cut off the fluid flowing of tested heat interchanger 1 opposite side.The fluid temperature (F.T.) (i.e. the fluid temperature (F.T.) of primary side fluid supply apparatus 2 outflow) controlling to flow into A point is 10 DEG C, and the temperature of inflow heat exchanger is 20 DEG C, and the flow flowing through heat interchanger is 10kg/s, when reaching stable, then has
0＝F2*C(T4-T3)-W+Q
leak
W-Q
leak＝F2*C(T4-T3)
As example, then make
W-Q
leak＝1.958kW,C＝4.1888kJ/kg℃，
T1＝20℃，T2＝0.490/10/4.1844+20＝20.012℃，T3＝10℃，T4≈T2＝20.012℃，
F2＝1.958/4.1888/(20.012-10)＝0.0467kg/s
The uncertainty of measurement that can be obtained shaft power by table five is 0.0277kW (K=2).
Then, start to test.The fluid temperature (F.T.) controlling to flow into A point is still 10 DEG C, and the temperature of inflow heat exchanger is 20 DEG C, and the flow flowing through heat interchanger is 10kg/s, when reaching stable, then has
Q＝F2*C(T4-T3)-W+Q
leak+q
As example, then make
W-Q
leak＝1.958kW
q＝0.490kW
T1＝20℃，T2＝21℃，T3＝10℃，T4≈T2＝21℃，
F2＝(1.958+41.840)/4.1883/(21-10)＝0.951kg/s
The uncertainty of measurement that can be obtained heat exchange amount by table six is 0.573kW (k=2).
This shows, although the precision of temperature sensor does not improve, by primary side fluid supply apparatus can by small for heat exchanger inlet and outlet less time measuring accuracy significantly improve.
In a first embodiment, the position of flow controller can also be changed according to actual needs, if entrance A is near the first entrance of tested heat interchanger, outlet B is near the first outlet of tested heat interchanger, flow controller is located between the first outlet of tested heat interchanger and outlet B, first temperature sensor is located between the first entrance of tested heat interchanger and entrance A, second temperature sensor is located between the entrance of flow controller and first of tested heat interchanger export, and at this moment needs to be provided with one the 4th temperature sensor in the porch of primary side fluid supply apparatus.
In the second embodiment of the present invention, primary side fluid supply apparatus is connected with secondary side fluid circulating device by an Intermediate Heat Exchanger 3, wherein the outlet of primary side fluid supply apparatus 2 is communicated with the first entrance of Intermediate Heat Exchanger 3, the entrance of primary side fluid supply apparatus 2 and the first outlet of Intermediate Heat Exchanger 3, the outlet of secondary side fluid circulating device is communicated with the second entrance of Intermediate Heat Exchanger 3, the entrance of secondary side fluid circulating device and the second outlet of Intermediate Heat Exchanger 3.The fluid flowed out by controlling primary side fluid supply apparatus 2 makes the fluid temperature (F.T.) at every turn flowing into tested heat interchanger 1 remain at same temperature.
This embodiment is applicable to the situation of fluid temperature (F.T.) close to transformation temperature of the first entrance of tested heat interchanger 1, and the water temperature as the first entrance of tested heat interchanger 1 is 1 DEG C, and now primary side fluid supply apparatus cannot adopt the water of-10 DEG C to flow into A point.Therefore, adopt Intermediate Heat Exchanger and adopt known physical property and away from the some fluid of phase transformation at the opposite side of Intermediate Heat Exchanger, such as glycol water, can the heat exchange amount of the tested heat interchanger of indirect inspection by the heat exchange amount measuring glycol water.
Certainly, tested heat interchanger also may be used for realizing refrigerating function, assuming that the mass rate of water is 10kg/s, the inlet temperature T1 of water is 21 DEG C, and outlet temperature T2 is 20 DEG C, and the specific heat at constant pressure of 20.5 DEG C of water is 4.1840kJ/kg DEG C, then heat exchange amount is Q=10 × (21-20) × 4.1840=41.840kW, now, desirable T3=30 DEG C, equally also can obtain and record high-precision heat exchange amount result.
In the above two embodiments, from analysis of measurement errors, q also belongs in a small amount, and when heat interchanger resistance is very little, this part can directly be ignored.
For the shaft power of pump, on the input shaft of pump, torque rotational speed meter can be installed, so just directly can measure the shaft power of pump.And for the flow control of heat interchanger side, by changing revolution speed, but flow can not be changed by a variable valve.
Above-mentioned first-class gauge and second gauge can be mass flowmeters, also can be electromagnetic flowmeters.
In the present invention, primary side fluid supply apparatus can comprise pump, flowrate control valve, heating refrigeratory, and as shown in Figure 3, heating refrigeratory is a common electric heater and cooling unit, this composition can be built to those skilled in the art easily, does not add detailed description at this.
Above by specific embodiment to invention has been detailed description, this embodiment is only preferred embodiment of the present invention, and it not limits the invention.Without departing from the principles of the present invention, the equivalent replacement that those skilled in the art makes and improvement, all should be considered as in the technology category protected in the present invention.
Claims (15)
1. improve the system that heat interchanger heat exchange measures accuracy of measurement under micro-temperature difference condition, it is characterized in that, comprise tested heat interchanger, secondary side fluid circulating device and primary side fluid supply apparatus;
Described tested heat interchanger comprises the first entrance, the first outlet, the second entrance and the second outlet, wherein the first entrance is connected with described secondary side fluid circulating device with the first outlet, second entrance and the second outlet are flowed into by another heat exchanging fluid and flow out, first entrance of described tested heat interchanger is provided with one first temperature sensor, first outlet of tested heat interchanger is provided with one second temperature sensor, and a first-class gauge is located at the first entrance of tested heat interchanger or the first outlet of tested heat interchanger;
Described secondary side fluid circulating device has flow controller, entrance A and outlet B, and wherein entrance A is connected by a connecting line with outlet B, and described flow controller makes the fluid flow constant of inflow tested heat interchanger first entrance;
Described primary side fluid supply apparatus is communicated with secondary side fluid circulating device, and exit is provided with a three-temperature sensor, one second gauge is located at porch or the exit of primary side fluid supply apparatus, described primary side fluid supply apparatus provides the fluid of steady temperature and flow, and the fluid flow provided by controlling primary side fluid supply apparatus makes the fluid temperature (F.T.) of inflow tested heat interchanger first entrance constant.
2. under micro-temperature difference condition according to claim 1, improve the system that heat interchanger heat exchange measures accuracy of measurement, it is characterized in that, described entrance A is near the first entrance of tested heat interchanger, outlet B is near the first outlet of tested heat interchanger, described flow controller is located between the first entrance of tested heat interchanger and entrance A, described first temperature sensor is located between the outlet of flow controller and the first entrance of tested heat interchanger, and the second temperature sensor is located between the first outlet of tested heat interchanger and outlet B.
3. under micro-temperature difference condition according to claim 1, improve the system that heat interchanger heat exchange measures accuracy of measurement, it is characterized in that, described entrance A is near the first entrance of tested heat interchanger, outlet B is near the first outlet of tested heat interchanger, described flow controller is located between the first outlet of tested heat interchanger and outlet B, described first temperature sensor is located between the first entrance of tested heat interchanger and entrance A, second temperature sensor is located between the entrance of flow controller and first of tested heat interchanger export, the porch of described primary side fluid supply apparatus is provided with one the 4th temperature sensor.
4. under micro-temperature difference condition according to claim 1, improve the system that heat interchanger heat exchange measures accuracy of measurement, it is characterized in that, described primary side fluid supply apparatus is directly communicated with secondary side fluid circulating device, wherein the outlet of primary side fluid supply apparatus is connected with the entrance A of secondary side fluid circulating device, the entrance of primary side fluid supply apparatus is connected with the outlet B of secondary side fluid circulating device, the fluid part flowed out from the outlet B of secondary side fluid circulating device flows into primary side fluid supply apparatus, flowed into the first entrance of tested heat interchanger by flow controller after another part flows back to the fluid chemical field that the entrance A of secondary side fluid circulating device and primary side fluid supply apparatus provide, and it is identical with the fluid flow flowing into primary side fluid supply apparatus from secondary side fluid circulating device from the fluid flow of primary side fluid supply apparatus inflow secondary side fluid circulating device.
5. under micro-temperature difference condition according to claim 1, improve the system that heat interchanger heat exchange measures accuracy of measurement, it is characterized in that, described primary side fluid supply apparatus is directly communicated with secondary side fluid circulating device, wherein the outlet of primary side fluid supply apparatus is connected with the outlet B of secondary side fluid circulating device, the entrance of primary side fluid supply apparatus is connected with the entrance A of secondary side fluid circulating device, the fluid chemical field rear portion that the fluid flowed out from the outlet B of secondary side fluid circulating device and primary side fluid supply apparatus provide flows back to primary side fluid supply apparatus, another part is flowed into the entrance A of secondary side fluid circulating device and is flowed into the first entrance of tested heat interchanger by flow controller, and the fluid flow flowing back to primary side fluid supply apparatus is identical with the fluid flow that primary side fluid supply apparatus provides.
6. under micro-temperature difference condition according to claim 1, improve the system that heat interchanger heat exchange measures accuracy of measurement, it is characterized in that, described primary side fluid supply apparatus is connected with secondary side fluid circulating device by an Intermediate Heat Exchanger, wherein the outlet of primary side fluid supply apparatus is communicated with the first entrance of Intermediate Heat Exchanger, the entrance of primary side fluid supply apparatus and the first outlet of Intermediate Heat Exchanger, the outlet B of secondary side fluid circulating device is communicated with the second entrance of Intermediate Heat Exchanger, the entrance A of secondary side fluid circulating device and the second outlet of Intermediate Heat Exchanger, the porch of described primary side fluid supply apparatus is provided with one the 4th temperature sensor.
7. under micro-temperature difference condition as claimed in any of claims 1 to 5, improve the system that heat interchanger heat exchange measures accuracy of measurement, it is characterized in that, be provided with one first pressure transducer between the outlet of described flow controller and the first entrance of tested heat interchanger, between the outlet of secondary side fluid circulating device and first of tested heat interchanger exports, be provided with one second pressure transducer.
8. improve the system that heat interchanger heat exchange measures accuracy of measurement under the micro-temperature difference condition according to claim 4 or 5, it is characterized in that, the porch of described primary side fluid supply apparatus is provided with one the 4th temperature sensor.
9. improve heat interchanger heat exchange under micro-temperature difference condition as claimed in any of claims 1 to 6 and measure the system of accuracy of measurement, it is characterized in that, described flow controller is water pump or water pump and variable valve.
10. improve the system that heat interchanger heat exchange measures accuracy of measurement under micro-temperature difference condition as claimed in any of claims 1 to 6, it is characterized in that, described primary side fluid supply apparatus comprises pump, flowrate control valve, heating refrigeratory.
The method that 11. 1 kinds of systems improving heat interchanger heat exchange measurement accuracy of measurement under adopting micro-temperature difference condition as claimed in claim 1 realize, is characterized in that,
First temperature sensor monitors of secondary side fluid circulating device flows into the fluid temperature (F.T.) of tested heat interchanger first entrance, second temperature sensor monitors exports the fluid temperature (F.T.) flowed out from tested heat interchanger first, first-class gauge monitoring stream enters tested heat interchanger first entrance or exports the fluid flow flowed out from tested heat interchanger first; The three-temperature sensor of primary side fluid supply apparatus monitors the fluid temperature (F.T.) flowed out from primary side fluid supply apparatus, the fluid flow that the monitoring of second gauge flows into primary side fluid supply apparatus or flows out from primary side fluid supply apparatus;
The fluid temperature (F.T.) flowing into tested heat interchanger first entrance remains at same probe temperature, the fluid flow that the flow controller of secondary side fluid circulating device controls to flow into tested heat interchanger first entrance remains on same test traffic, and the fluid temperature (F.T.) that primary side fluid supply apparatus provides remains on same supplying temperature;
Heat-insulation and heat-preservation is carried out to whole system, when system stable operation is in thermal equilibrium state, so
Q＝F1*C1*(T2-T1)＝F2*C2*(T2-T3)-W+Q
leak+q≈F2*C2*(T2-T3)-W+q
W＝(M*H1*S)/(367.7*E)
q＝(M*H2*S)/367.7
Wherein, Q is the heat exchange amount of tested heat interchanger, F1 is the mass rate of the fluid that tested heat interchanger first entrance flows into, C1 is the mean specific heat of the fluid that tested heat interchanger first entrance flows into, T1 is the temperature of the fluid that tested heat interchanger first entrance flows into, T2 is the temperature of the fluid that the outlet of tested heat interchanger first is flowed out, the mass rate of the fluid that F2 provides for primary side fluid supply apparatus, C2 is the mean specific heat of the fluid that primary side fluid supply apparatus flows out, T3 is the temperature of the fluid that primary side fluid supply apparatus flows out, W is the power of the flow controller in secondary side fluid circulating device, Q
leakfor pipeline leaks heat, q is the heat energy that heat interchanger inner fluid transforms because of friction, and M is the volumetric flow rate of the fluid that tested heat interchanger first entrance flows into, and H1 is lift, S is the specific density of the fluid that tested heat interchanger first entrance flows into, E is the efficiency of pump in flow controller, H2 is the design resistance of tested heat interchanger.
Improve the method that heat interchanger heat exchange measures accuracy of measurement under 12. micro-temperature difference conditions according to claim 11, it is characterized in that,
When primary side fluid supply apparatus is directly communicated with secondary side fluid circulating device, the outlet of primary side fluid supply apparatus is connected with the entrance A of secondary side fluid circulating device, the entrance of primary side fluid supply apparatus is connected with the outlet B of secondary side fluid circulating device, the fluid part flowed out from the outlet B of secondary side fluid circulating device flows into primary side fluid supply apparatus, another part flows back to the entrance A of secondary side fluid circulating device, and the fluid flow flowing into primary side fluid supply apparatus is identical with the fluid flow flowed out from primary side fluid supply apparatus; Control fluid that primary side fluid supply apparatus provides and export the fluid temperature (F.T.) that blending ratio that B flows back to the fluid of secondary side fluid circulating device entrance A makes tested heat interchanger first entrance flow into from secondary side fluid circulating device and remain at same probe temperature;
When primary side fluid supply apparatus is connected with secondary side fluid circulating device by an Intermediate Heat Exchanger, the outlet of primary side fluid supply apparatus is communicated with the first entrance of Intermediate Heat Exchanger, the entrance of primary side fluid supply apparatus and the first outlet of Intermediate Heat Exchanger, the outlet of secondary side fluid circulating device is communicated with the second entrance of Intermediate Heat Exchanger, the entrance of secondary side fluid circulating device and the second outlet of Intermediate Heat Exchanger.
Improve the method that heat interchanger heat exchange measures accuracy of measurement under 13. micro-temperature difference conditions according to claim 11, it is characterized in that, the 4th temperature sensor monitors flows into the fluid temperature (F.T.) of primary side fluid supply apparatus from secondary side fluid circulating device, so
Q＝F1*C1*(T2-T1)＝F2*C2*(T4-T3)-W+Q
leak+q
Wherein, T4 is the temperature of the fluid that primary side fluid supply apparatus flows into.
Improve the method that heat interchanger heat exchange measures accuracy of measurement under 14. micro-temperature difference conditions according to claim 11, it is characterized in that,
Tested heat interchanger is carried out insulation, and makes without heat exchanging fluid between the second entrance of tested heat interchanger and the second outlet, when system stable operation,
Q＝q
W-Q
leak≈W＝F2*C2*(T2-T3)
The uncertainty of measurement of the power of pump in flow controller in secondary side fluid circulating device is calculated, wherein T2=q/F1/C1+T1 according to the value of F2, T2, T3, standard uncertainty, probability distribution, sensitivity coefficient and partial uncertainty;
The uncertainty of measurement of the heat energy that tested heat interchanger inner fluid transforms because of friction is calculated according to the value of F1, H2, standard uncertainty, probability distribution, sensitivity coefficient and partial uncertainty;
According to F2, T1, T2, W-Q
leak, the value of q, standard uncertainty, probability distribution, sensitivity coefficient, partial uncertainty calculate the uncertainty of measurement of the heat exchange amount of tested heat interchanger.
Improve the method that heat interchanger heat exchange measures accuracy of measurement under 15. micro-temperature difference conditions according to claim 11, it is characterized in that, described flow controller is water pump, is measured the shaft power of water pump by the torque rotational speed meter be arranged in water pump input shaft.
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