CN117619471A - Condensation experimental device based on array jet impact - Google Patents

Abstract

The invention discloses a condensation experimental device based on array jet impact, which is mainly used for experimental research on the local condensation heat transfer coefficient in a heat exchange tube. It is characterized by including a test section, an air supply system and a refrigerant circulation system. The test section is composed of a jet device, a measured channel and a sensor. The air supply system provides the required cooling air for the jet device, and the refrigerant circulation system provides the required state of refrigerant for the measured channel. The jet plate in the jet device is used to generate a uniform jet, and the cooling air impacts the wall of the measured channel and exchanges heat with the wall to achieve condensation of the vapor refrigerant in the measured channel. Relying on the air supply system to control the jet air state, the condensation experimental device can simulate different condensation conditions. The invention meets the experimental conditions of local condensation heat transfer coefficient. At the same time, the condensation experiment device has a wide adjustment range, a fast response speed, and simple control, and can effectively improve the stability of the condensation experiment and the reliability of data.

Description

A condensation experimental device based on array jet impact

Technical field

The invention relates to a condensation experiment device, specifically an array impact jet device and its working mode, which can obtain the local condensation heat transfer coefficient in a measured channel, and belongs to the technical field of condensation experiments.

Background technique

In-tube flow condensation is a common two-phase heat transfer process that often occurs in various industrial applications, such as air conditioning systems and spacecraft thermal control systems. As cooling system heat loads continue to increase, effective heat removal is critical to maintaining reliable system performance. The condenser, as the core component in two-phase heat exchange, needs to have higher heat transfer efficiency under weight and size constraints. In order to further improve the performance of the condenser, methods to enhance condensation heat transfer in the tube have been widely studied. Therefore, a condensation experimental device is needed to conduct experimental research on different reinforced tubes in order to understand their condensation heat transfer characteristics. In addition, the condensation experimental device can also verify the design and provide guidance for the design and selection of heat exchange tubes in the condenser. At present, most condensation experiments use jacket cooling devices, which are generally used to measure the average condensation heat transfer coefficient in the tube. However, the study of the condensation heat transfer mechanism and the establishment of the condensation model require accurate local values of the condensation heat transfer coefficient in the tube, and now The traditional casing condensation experimental device cannot meet the requirements for accurate measurement of local condensation heat transfer coefficient.

In view of the shortcomings of condensation experiment technology, the present invention proposes a condensation experiment device based on array jet impact. As an efficient cooling method, air impact jet cooling has strong heat transfer effect and can meet the cooling requirements in condensation experiments. When conducting experiments on measured channels of different sizes, a single-hole impact jet cannot meet the uniform coverage of the target surface, so the use of multi-hole array jet impact can meet the cooling requirements of a large area. The porous array impact jet can uniformly cool the heat exchange surface, but the jet cooling effect requires research and design of the geometric parameters of the porous array. In addition, for condensation experiments, the state of the cooling medium has an important impact on the stability of the condensation process. Each parameter of the cooling medium needs to be stable and respond quickly during adjustment.

Contents of the invention

In view of the limitations of condensation experiment technology, the present invention proposes a condensation experiment device based on array jet impact, which provides a new method for experimental research on local condensation heat transfer coefficient in the measured channel.

In order to achieve the above objectives, the present invention provides a condensation experimental device based on array jet impact and a corresponding working method, including a test section, an air supply system and a refrigerant circulation system. The test section is composed of a jet device, a tested channel and a sensor; in the jet device, a closed pressure stabilizing chamber is set up in the jet device, and an air inlet flute-shaped tube is set above the pressure stabilizing chamber. The air inlet flute-shaped tube is connected with the air supply. For system connection, air supply holes are evenly arranged on the air inlet flute-shaped tube located inside the pressure stabilizing chamber; a jet plate is installed on the lower wall of the pressure stabilizing chamber, and jet holes are evenly arranged on the jet plate; the jet holes are perpendicular to the wall of the measured channel and maintained at a certain distance ; Limit baffles are arranged on both sides of the jet plate, and the limit baffles form a fixed jet area between the jet plate and the channel under test; wall temperature sensors are evenly arranged on the wall of the channel under test, and are located at the entrance and exit of the channel under test. It is equipped with an inlet refrigerant temperature sensor, an inlet refrigerant pressure sensor, an outlet refrigerant temperature sensor and an outlet refrigerant pressure sensor;

The cooling air provided by the low-temperature air source in the air supply system flows through the air heater and is divided into two paths. One path enters the bypass flow regulating valve and is connected to the atmosphere, and the other path enters the jet air inlet flute in the jet device. The components are connected by air supply pipelines, and a jet air supply mass flow meter and a jet air supply temperature sensor are arranged on the air supply pipeline before entering the jet device to feedback the jet air state;

The refrigerant circulation system is composed of a liquid storage tank, a gear pump, a flow meter, an evaporator, a channel to be measured and a condenser, which are connected in sequence through pipelines to form a circulation loop. The loop is filled with the working fluid to be measured, and is placed at the entrance of the evaporator. A channel refrigerant temperature sensor and a channel refrigerant pressure sensor are arranged, and the cooling unit provides cooling liquid for the condenser.

Further, the jet holes are evenly arranged on the wall surface of the jet plate, the diameter of the jet holes ranges from 1 to 2 mm, the distance between adjacent jet holes and the ratio of the jet hole diameters ranges from 4 to 6, and the distance between the jet plate and the target surface and the ratio of the jet hole diameters range 6 to 8, condensing jets for measured channels of different sizes can be effectively realized by adjusting the jet hole parameters.

Further, the limit baffle limits the measured channel directly below the jet hole, and a jet area with a fixed jet height is formed between the jet plate and the measured channel. The value of the jet height is 3 to 5 times the diameter of the jet hole.

Further, uniform air supply holes are arranged on the upper wall of the jet air inlet flute-shaped tube. The diameter of the air supply holes is 4 to 6 mm. The ratio of the axial spacing of the air supply holes to the diameter of the air supply holes is in the range of 4 to 6. The radial angle of the air supply holes is in the range of 45° to 45°. 60°, uniform air intake can be achieved by adjusting the air supply hole parameters, and the flow field stabilization in the pressure stabilizing chamber can be accelerated.

Furthermore, the air heater is used to adjust the jet inlet air temperature, and the bypass flow adjustment valve is used to adjust the jet air supply flow. This design enables rapid adjustment of different jet working conditions and facilitates switching of condensation experimental working conditions.

Further, the wall temperature sensor is arranged in the jet area of the measured channel, and the ratio between the spacing between the wall temperature sensors and the jet hole diameter ranges from 20 to 30, which is used to feed back the local wall temperature of the measured channel.

Furthermore, the cooling unit can provide the condenser with an adjustable constant-temperature coolant of -25°C to 50°C, and the adjustable coolant temperature can control the condensation heat exchange temperature difference in the condenser, thereby adjusting the working pressure in the refrigerant circulation system. , the coolant temperature is fed back through the coolant temperature sensor.

The beneficial effects of the present invention compared to the prior art are:

(1) This invention provides a new method for the experimental study of local condensation heat transfer coefficient in the tube. Based on the heat transfer characteristics of array jet impact, it ensures a uniform jet impact heat transfer coefficient on the surface of the measurement channel. According to the collected jet air and the measured The temperature difference on the channel wall is used to calculate the local condensation heat flux density, which solves the problem that the local heat flux density cannot be accurately measured. Based on this, the local condensation heat transfer coefficient in the measured channel is further calculated.

(2) The control logic of the condensation experimental device of the present invention is simple, the system response speed is fast, the working stability is high, the components are easy to assemble and replace, and is suitable for experimental research on a wide range of condensation working conditions and measured channels of different sizes.

Description of drawings

Figure 1 is a schematic diagram of the principle of the condensation experimental device based on array impact jet according to the present invention;

Figure 2 is a connection assembly diagram of the test section in the present invention;

Figure 3 is a cross-sectional view of the jet device in the present invention;

Figure 4 is a bottom view of the jet device in the present invention;

Figure 5 is a perspective view of the distribution of wall temperature sensors according to the present invention;

Figure 6 is a schematic diagram of the jet air supply flute type tube in the test section of the present invention;

Figure 7 is a schematic diagram of the air supply system of the present invention;

Figure 8 is a schematic diagram of the principle of the calibration experiment system of the present invention;

Figure 9 is an assembly perspective view of the target plate of the present invention;

1-Test section in the picture:

11-jet device, 12-tested channel, 13-jet air inlet flute, 14-air supply hole, 15-pressure stabilizing chamber, 16-jet plate, 17-jet hole, 18-limit baffle, 19- Wall temperature sensor, 110-inlet refrigerant temperature sensor, 111-inlet refrigerant pressure sensor, 112-outlet refrigerant temperature sensor, 113-outlet refrigerant pressure sensor;

2-Air supply system: 21-low temperature air source, 22-air heater, 23-bypass flow control valve, 24-air supply pipeline, 25-jet air supply mass flow meter, 26-jet air supply temperature sensor;

3-Refrigerant circulation system: 31-liquid storage tank, 32-gear pump, 33-flow meter, 34-evaporator, 35-condenser, 36-cooling unit, 37-coolant temperature sensor;

4-Jet device calibration system: 41-metal target plate, 42-metal target plate wall temperature sensor, 43-heating film, 44-adjustable DC power supply.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings.

The invention provides a condensation experimental device based on array jet impact, including a test section 1, an air supply system 2 and a refrigerant circulation system 3. As shown in Figure 1, the air supply system 2 provides the required jet air for the test section 1 , the refrigerant circulation system 3 provides the required refrigerant for the test section 1. The cooling air flows through the jet device 11 and hits the wall of the channel 12 under test. The cooling air exchanges heat with the wall and takes away the heat of the refrigerant, thereby condensing the vapor refrigerant in the channel 12 under test.

The assembly relationship of the test section 1 is shown in Figure 2. The jet device 11 is above the measured channel 12, and an inlet refrigerant temperature sensor 110, an inlet refrigerant pressure sensor 111, and an outlet refrigeration sensor are respectively arranged at the entrance and exit of the measured channel 12. agent temperature sensor 112 and outlet refrigerant pressure sensor 113; in the jet device 11, as shown in Figure 3, the jet air provided by the air supply system 2 flows through the jet air inlet flute tube 13, and passes through the jet air inlet flute tube 13. The air supply hole 14 on the upper wall enters the pressure stabilizing chamber 15, and then the jet air impacts to the wall of the measured channel 12 through the jet hole 17 on the jet plate 16; the limiting baffles 18 arranged on both sides of the jet plate are shown in Figure 4. The function of the position baffle is to limit the measured channel 12 directly below the jet hole 17, and to limit the space between the jet plate and the measured channel to a jet area with a fixed jet height. By adjusting the limit baffle 17, the jet height can be changed. To meet the requirements of different jet areas, the value of the jet height is 3 to 5 times the diameter of the jet hole; wall temperature sensors 19 are evenly arranged on the wall of the measured channel 12, as shown in Figure 5, where the wall temperature sensor 19 is arranged in the same area as the jet The areas are consistent, and the ratio between the distance between the wall temperature sensors 19 and the diameter of the jet hole 17 ranges from 20 to 30.

In order to achieve uniform array jet impact, as shown in Figure 4, the jet holes 17 are evenly arranged on the wall surface of the jet plate 16, the diameter of the jet holes ranges from 1 to 2 mm, the spacing between adjacent jet holes and the ratio of the diameter of the jet holes range from 4 to 6, the jet plate The ratio between the distance from the target surface and the jet hole diameter ranges from 6 to 8. By adjusting the jet hole parameters, condensing jets can be effectively achieved for the measured channels of different sizes. As shown in Figures 3 and 6, uniform air supply holes 14 are arranged on the upper wall of the jet air inlet flute tube 13. The diameter of the air supply holes is 4 to 6 mm. The ratio between the axial spacing of the air supply holes and the diameter of the air supply holes is in the range of 4 to 6. The diameter of the air supply holes is 4 to 6 mm. With an angle of 45° to 60°, uniform air intake can be achieved by adjusting the air supply hole parameters, speeding up the stability of the flow field in the pressure stabilizing chamber 15 and ensuring uniform jet flow of the jet plate.

The air supply system 2 consists of a low-temperature air source 21, an air supply pipeline 22, an air heater 23, a bypass flow regulating valve 24, a jet air supply mass flow meter 25 and a jet air supply temperature sensor 26. As shown in Figure 7, the low temperature The air provided by the air source 21 flows through the air heater 23 and is divided into two paths. One path is connected to the bypass flow regulating valve 24. The outlet of the bypass flow regulating valve 24 is connected to the environment; the other path is connected to the test section 1 for jet air supply. The mass flow meter 25 and the air supply temperature sensor 26 are respectively used to monitor the air supply flow and air supply temperature of the road. The air heater 23 is generally in a non-heating state, and the bypass flow regulating valve 24 is generally in a normally closed state. When it is necessary to reduce the jet impact cooling intensity, priority is given to increasing the opening of the bypass flow regulating valve 24 to reduce the jet air supply flow; When the opening of the bypass flow regulating valve 24 is at its maximum, but the jet impact cooling intensity still needs to be reduced, the heating power of the air heater 23 is increased to increase the jet air supply temperature.

The refrigerant circulation system 3 provides the required refrigerant for the measured channel 12. As shown in Figure 1, the liquid storage tank 31, the gear pump 32, the flow meter 33, the evaporator 34, the measured channel 12, and the condenser 35 pass through the pipeline. Connect in turn to form a circular loop. The evaporator 34 uses a parallel flow porous flat tube heat exchanger. An electric heating film is arranged on the wall of the heat exchanger. By controlling the electric heating power, the superheat degree of the refrigerant at the inlet of the measured channel 12 can be quickly adjusted. The cooling unit 36 can provide the condenser 35 with an adjustable constant-temperature coolant of -25°C to 50°C. By adjusting the coolant temperature, the condensation heat exchange temperature difference in the condenser 35 is controlled, thereby adjusting the working pressure in the refrigerant circulation system and cooling. The fluid temperature is fed back via the coolant temperature sensor 37 .

The experimental method follows the steps:

Step 1. Confirm the size of the measured channel 12 (for example: jet impact area area A _air , heat transfer area of the inner wall of the measured channel A _h ), and select the condensation experiment working condition range (for example: minimum saturation temperature T _sat,min ) , calculate the required maximum condensation load Q _cold.max ; confirm the state range of the jet air provided by the air supply system 2 (air supply flow rate m and air supply temperature T _air ); refer to the existing relevant condensation research results, and based on the selected experiments The condensation heat transfer coefficient h _tp,pre in the measured channel is estimated under the working condition (for example, for a straight microchannel, assume h _tp,pre =3000kW/m ² K), according to the formula Q _cold,max =h _tp,pre A _h (T _w,pre -T _sat,min ) estimates the wall temperature T _w,pre , and then according to the formula Estimate the required minimum jet impact heat transfer coefficient value h _j,pre (the air supply temperature T _air takes the minimum value).

Step 2: Based on the estimated minimum jet impact heat transfer coefficient h _{j, pre} and the maximum value of the air supply flow rate m, design the parameters of the air supply hole 14 on the upper wall of the jet inlet flute 13 in the jet device 11 and the jet hole on the jet plate 16 17 parameters and the jet height limited by the limit baffle 18, verify the design through CFD simulation, requiring h _j,CFD ≥1.2h _j,pre , iteratively select a design solution that meets the requirements, process the required parts, and assemble the jet device.

Step 3: Set up a calibration experiment system. As shown in Figure 8, the calibration experiment system includes the jet device calibration system 4 and the air supply system 2. The purpose is to verify whether the air supply system 2 and the jet device 11 meet the condensation experiment requirements and ensure that the entire jet flow is maintained. Within the range of working conditions, the calibration of the jet impact heat transfer coefficient is completed; in the calibration experiment, the outer dimensions of the metal target plate 41 are consistent with the measured channel 12, and an S-shaped electric heating film 43 is pasted on the back of the metal target plate to provide uniform heat flow q _h , as shown in Figure 9, the heating film area is consistent with the jet area, and a metal target plate wall temperature sensor 42 is arranged in the heating film gap. The ratio of the spacing between the metal target plate wall temperature sensors 42 to the diameter of the jet hole 17 ranges from 20 to 30. ;

Step 4. Verification 1: The jet uniformity of the jet device is verified by comparing the difference between the local wall temperatures T _w,i of the metal target surface. The inspection standard is that the difference between the local wall temperatures does not exceed the measurement uncertainty of the temperature sensor itself. Spend;

Step 5. Verification 2: Whether the jet device meets the requirements of the condensation experiment conditions, by comparing the actual jet impact heat transfer coefficient h _j with the minimum jet impact heat transfer coefficient h _j,pre estimated in step 1, the inspection standard is h _j ≥h _j,pre (jet working condition: maximum air supply flow rate m, minimum air supply temperature T _air ); the actual jet impact heat transfer coefficient h _j is calculated according to the formula h _j =q _h /(T _wm -T _air )( T _wm is the average value of T _w,i ).

Step 6. After passing the verification, conduct multiple sets of jet impact experiments within the full range of jet working conditions, complete the experimental calibration of the jet device, and obtain the relationship between the actual jet impact heat transfer coefficient h _j and the jet air Re and Pr: h _j =aRe ^b Pr ^1/3 , the constant coefficients a and b in the formula are determined based on the calibration experimental results. The jet air Re is defined as: (m is the jet air mass flow rate, d is the equivalent diameter of the jet hole, A is the total flow cross-sectional area of all jet holes, μ is the dynamic viscosity), and the jet air Pr is a physical parameter determined by the jet air temperature.

Step 7: After obtaining the calculation formula of the actual jet impact heat transfer coefficient h _j , as shown in Figure 1, set up a condensation experiment system to carry out the condensation experiment. According to the formula: q _k = h _j (T _w,k -T _air ) (q _k is the local condensation heat flux density, h _j is the jet impact heat transfer coefficient, T _air is the jet air temperature, T _w,k is the measured channel The local wall temperature) can be used to obtain the condensation heat flux density corresponding to the local position k in the current state, and then according to (h _tp,k is the local condensation heat transfer coefficient, T _sat,k is the local saturation temperature of the refrigerant) The condensation heat transfer coefficient corresponding to the local position k in the measured channel (14) in the current state can be obtained, and the refrigerant is partially saturated. The temperature T _sat,k is determined by the local saturation pressure. There are four calculation methods: inlet and outlet average assumption, linear distribution assumption, pressure drop model prediction and direct measurement of absolute pressure. The specific choice is based on the actual situation.

Step 8. Switching the condensation working condition can be obtained by changing the jet air parameters (jet air temperature or jet air supply flow rate); when reducing the condensation heat flow density (increasing the jet air temperature or reducing the jet air supply flow rate), it is necessary to appropriately reduce The coolant temperature provided by the small cooling unit 36 is, on the contrary, the coolant temperature needs to be increased to maintain the stability of the working pressure in the refrigerant circulation system.

The above are only preferred embodiments of the present invention. It should be pointed out that for those of ordinary skill in the art, several improvements can be made without departing from the principles of the present invention, and these improvements should also be regarded as the present invention. scope of protection.

Claims (7)

1. An experimental device for condensation heat transfer coefficient based on array jet impact, characterized in that it includes a test section (1), an air supply system (2) and a refrigerant circulation system (3); wherein the test section (1 ) includes a jet device (11), a measured channel (12) and a sensor; the jet device (11) includes a closed pressure stabilizing chamber (15), and an air intake flute-shaped tube (13) is arranged above the pressure stabilizing chamber (15) , the air intake flute (13) is connected with the air supply system (2), and air supply holes are evenly provided on the air intake flute (13) located inside the pressure stabilizing chamber (15); the lower wall of the pressure stabilizing chamber (15) is provided with Jet plate (16), jet holes (17) are evenly arranged on the jet plate (16); the jet holes (17) are perpendicular to the wall of the measured channel (12) and kept at a certain distance; limits are arranged on both sides of the jet plate (16) The baffle (18) and the limit baffle (16) form a fixed jet area between the jet plate (16) and the measured channel (12); wall temperature sensors (19) are evenly arranged on the wall of the measured channel (12) , an inlet refrigerant temperature sensor (110), an inlet refrigerant pressure sensor (111), an outlet refrigerant temperature sensor (112) and an outlet refrigerant pressure sensor (113) are respectively arranged at the entrance and exit of the measured channel (12). ; The cooling air provided by the medium and low temperature air source (21) of the air supply system (2) flows through the air heater (22) and is divided into two paths. One path enters the bypass flow regulating valve (23) and is connected to the atmosphere, and the other path Enter the jet air inlet flute (13) in the jet device (11), and the components are connected by an air supply pipeline (24). A jet air supply mass flow meter (25) and The jet air supply temperature sensor (26) is used to feedback the status of the jet air; The refrigerant circulation system (3) includes a liquid storage tank (31), a gear pump (32), a flow meter (33), an evaporator (34), a measured channel (12) and a condenser (35) through pipelines They are connected in sequence to form a circulation loop, and the loop is filled with the working fluid to be measured; a channel refrigerant temperature sensor (37) and a channel refrigerant pressure sensor (38) are arranged at the entrance of the evaporator (34); the cooling unit (36 ) provides cooling liquid to the condenser (35), and a cooling liquid temperature sensor (37) is arranged before entering the condenser (35). 2. The experimental device according to claim 1, characterized in that the jet holes (17) are evenly arranged on the wall of the jet plate (16), the diameter of the jet holes (17) ranges from 1 to 2 mm, and the adjacent jet holes (17) ) The diameter ratio range is 4 to 6. By adjusting the parameters of the jet hole (17), the condensing jet for the measured channels of different sizes can be effectively realized. 3. The experimental device according to claim 1, characterized in that uniform air supply holes (14) are arranged on the upper wall of the jet air inlet flute-shaped tube (13), and the diameter of the air supply holes (14) is 4~6 mm. , the ratio between the axial spacing of the air supply holes (14) and the diameter of the air supply holes (14) ranges from 4 to 6, and the radial angle of the air supply holes (14) is 45° to 60°. 4. The experimental device according to claim 1, characterized in that the limiting baffle (18) limits the measured channel (12) directly below the jet hole (17), and the jet plate (16) is in contact with the measured channel. The jet area between the channels (12) is limited to a specific jet height, and the value of the jet height is 3 to 5 times the diameter of the jet hole (17). 5. The experimental device according to claim 1, characterized in that the air heater (22) is used to adjust the jet inlet air temperature, and the bypass flow adjustment valve (23) is used to adjust the jet air supply flow. 6. The experimental device according to claim 1, characterized in that the wall temperature sensor (19) is arranged in the jet area of the measured channel (12), and the distance between the wall temperature sensors (19) is consistent with the jet hole (19). 17) The diameter ratio range is 20~30, which is used to feedback the local wall temperature of the measured channel (12). 7. The experimental device according to claim 1, characterized in that the cooling unit (36) can provide the condenser (35) with adjustable constant-temperature coolant at -25°C~50°C, which is controlled by adjusting the coolant temperature. The condensation heat exchange temperature difference in the condenser (35) realizes the control of the refrigerant working pressure in the refrigerant circulation system (3), and the coolant temperature is fed back through the coolant temperature sensor (37).