A heat recovery circulation system with high heating energy efficiency

Abstract

The present invention discloses a heat recovery circulation system with high heating energy efficiency, comprising an economizer, an expansion valve respectively connected to the front and rear sides of the economizer, and an evaporator, a compressor, and a subcritical flow vortex heat exchanger connected in sequence. The subcritical flow vortex heat exchanger comprises an exchanger shell, an air inlet nozzle, a cold-end steam outlet, and a hot-end steam outlet. The cold-end steam outlet is directly connected to the economizer, the hot-end steam outlet is connected to the economizer through the front expansion valve, and the rear expansion valve outlet is connected to the evaporator, thereby forming a closed loop; the exchanger shell is in the shape of a long tube as a whole, and a heat exchange core tube is coaxially installed in the middle and rear part of the cavity. The heat exchange core tube divides the inner cavity of the exchanger shell into an energy separation zone and a cooling water zone. The front cavity of the exchanger shell is connected to the air inlet nozzle and serves as a steam vortex flow zone. It has the advantages of stronger heating capacity, low pressure ratio, high-temperature hot water, high heating energy efficiency, and reasonable design and layout.

Description

Technical Field

[0001] The present invention belongs to the technical field of low-temperature waste heat recovery, and in particular relates to a heat energy recovery circulation system with high heating energy efficiency. Background Art

[0002] In modern society, a large amount of low-temperature waste heat exists, such as heat dissipation in communication data centers, power generation cold-ends, and other industrial processes. This low-temperature heat is essentially dissipated into ambient heat sinks, resulting in significant energy waste. Direct reuse of this low-temperature heat is difficult, and often requires the necessary technical means, methods, and devices to collect, concentrate, and process it into high-temperature, high-quality heat for wider application.

[0003] like Figure 5 As shown, the existing heat pump heat energy recovery process mainly adopts a single-stage compression system, that is, evaporator A absorbs heat at low temperature → compressor B high pressure → condenser C1 releases heat at high temperature → expansion valve D is low temperature and low pressure → then returns to evaporator A to absorb heat at low temperature for a single-stage cycle, so as to achieve the purpose of collecting, concentrating and processing low-temperature heat energy into high-temperature heat energy. However, due to the influence of the thermophysical properties of the refrigerant (such as the critical temperature of R22 is 96℃ and the critical pressure is 4.99MPa) and the need for high heating energy efficiency, the pressure ratio is limited during the heating cycle of single-stage compression at a low pressure ratio, so the condensing temperature generally does not exceed t K =50℃ (i.e., high-temperature heat release temperature). Considering the logarithmic temperature difference of the condenser vapor-liquid heat transfer (about 10℃), the actual heating temperature is relatively low (about 40℃), which limits the application value and scope of low-temperature heat energy recovery.

[0004] In order to obtain a higher water temperature, such as Figure 6 As shown, a bipolar compression system is currently used, but the pressure ratio is increased. Although it can reach a high-temperature hot water of 65°C, the heating efficiency is low, resulting in high requirements for the material structure strength, thereby increasing the construction cost.

[0005] Regardless of whether it is a single-stage compression system or a bipolar compression system, a traditional condenser is usually used to achieve the high-temperature heat release function. The traditional condenser has a simple structure and uses a cooling medium to cool the high-temperature and high-pressure gaseous refrigerant. The fluid flow rate is generally 1m / s to 3m / s, and the heat release efficiency is low. Summary of the Invention

[0006] The present invention aims to provide a heat recovery circulation system with high heating energy efficiency, high heat release efficiency, and a subcritical flow state of refrigerant gas. It solves the problem that it is difficult to obtain high-temperature heating capacity at a low pressure ratio using a single-stage compression system, which limits the application value and scope of low-temperature heat recovery, and the problem that the pressure ratio of a bipolar compression system increases, resulting in low heating efficiency and high requirements for material structure strength.

[0007] To this end, the technical solution adopted by the present invention is: a high heating energy efficiency heat recovery circulation system, including an economizer, an expansion valve connected to the front and rear sides of the economizer respectively, and an evaporator, a compressor, and a subcritical flow vortex heat exchanger connected in sequence, the subcritical flow vortex heat exchanger includes an exchanger shell, an air inlet nozzle extending horizontally and laterally connected to the top of the exchanger shell, a cold end steam outlet centrally located at the front end of the exchanger shell and a hot end steam outlet centrally located at the rear end of the exchanger shell, the cold end steam outlet is directly connected to the economizer, the hot end steam outlet is connected to the economizer through the front expansion valve, and the rear expansion valve outlet is connected to the evaporator, thereby forming a closed loop; the exchanger shell is in the shape of a long tube as a whole, and the middle and rear parts of the cavity are coaxially arranged. A heat exchange core tube is installed, which divides the inner and outer inner cavity of the exchanger shell into an energy separation zone and a cooling water zone. The front cavity of the exchanger shell is connected to the air inlet nozzle, and serves as a gas vortex flow zone for high-speed tangential entry of high-pressure and high-temperature gas to form a high-speed vortex flow. When the gas spiraling into the energy separation zone is separated into an inner layer of low-temperature gas and an outer layer of high-temperature gas under the action of a high-speed centrifugal vortex, the gas in the outer layer of high-temperature gas in a subcritical flow state transfers heat with the cooling water zone with the help of the heat exchange core tube. The hot end gas outlet is used to export the low-temperature and high-pressure gas-liquid mixture condensed after the heat transfer of the outer layer of high-temperature gas, and the cold end gas outlet is used to export the low-temperature and low-pressure gas-liquid mixture condensed after the energy of the inner layer of low-temperature gas is exchanged with the outer layer of high-temperature gas.

[0008] As a preferred embodiment of the above scheme, the cold-end steam outlet and the hot-end steam outlet are respectively centrally located at the front and rear ends of the exchanger shell. The cold-end steam outlet is provided with a cold steam guide pipe extending axially from the outside of the front end of the exchanger shell to the energy separation zone. The cold steam guide pipe penetrates into the belly of the exchanger shell to facilitate the collection of the low-temperature and low-pressure steam-liquid mixture after the condensation of the inner layer of low-temperature gas. The design structure is reasonable.

[0009] It is further preferred that the transition section between the gas vortex flow zone and the heat exchange core tube is provided with a tapered tube connected from the inner wall of the exchanger shell to the front end of the heat exchange core tube. The tapered tube is used to seal the front end of the cooling water zone and guide the axial swirl of gas in the gas vortex flow zone to the energy separation zone, serving two purposes at one stroke. In addition, the inner diameter is contracted in the transition section, the gas is compressed, the pressure is increased, and the molecular vibration frequency is accelerated, thereby increasing the gas vortex speed and guiding the gas flow direction. The design is exquisite.

[0010] It is further preferred that the inner wall of the heat exchange core tube is spirally circled with metal inner spiral fins and the outer wall is spirally circled with metal outer spiral fins, so that the gas in the subcritical flow state in the high-temperature and high-pressure gas can transfer heat with the cooling water area with the help of the metal inner spiral fins and the metal outer spiral fins, and the spiral density can be flexibly changed according to the actual heat transfer requirements. The design is reasonable, and heat is transferred through the inner and outer fins to ensure efficient heat transfer.

[0011] It is further preferred that the metal inward-spiraling fins and the metal outward-spiraling fins are both made of porous metal. Compared with ordinary metal plates, under the same plate specifications, porous metal can greatly increase the contact heat exchange area of gas molecules by nearly 20 times, and also extend the heat exchange process inside and outside the heat exchange core tube, greatly improving the heat exchange capacity. Porous metal is mainly used for vibration reduction and sound absorption, but the large specific surface area of porous metal is rarely used. There is currently no precedent for its application to heat exchange equipment, and the material selection is clever.

[0012] It is further preferred that the outer ends of the metal outward-spiral fins are close to the inner wall of the exchanger shell, which increases the contact area between the cooling medium and the metal outward-spiral fins and improves the heat transfer effect. There is an axial and radial distance between the metal inward-spiral fins and the inner end of the cold steam guide tube, which effectively avoids the cold steam guide tube and the metal inward-spiral fins from colliding, causing mutual interference and affecting the heat transfer or cold air extraction effect. The layout is reasonable.

[0013] More preferably, the exchanger housing is radially provided with a cooling water inlet and a cooling water outlet at the front and rear ends corresponding to the cooling water zone, and adopts cold water cooling, which has low cost and reasonable design.

[0014] Further preferably, the hot end gas outlet diameter is located between the inner diameter of the heat exchange core tube and the cold end gas outlet diameter, and the design structure is reasonable to ensure that the low and high temperature stratified gases in the inner and outer layers flow out without confusion.

[0015] Further preferably, the rear end of the cold steam guide tube is provided with a conical inward-concave microporous plate, which can reduce the pressure of high-temperature and high-pressure gas molecules mixed with the inner layer of low-temperature gas, and has a reasonable structure.

[0016] Beneficial effects of the present invention:

[0017] (1) Compared with the single-stage compression system, which is difficult to obtain high-temperature heating capacity, resulting in limited application value and scope of low-temperature heat recovery, and the double-stage compression system with increased pressure ratio, resulting in low heating efficiency and high requirements for material structure strength, this scheme adopts a subcritical flow vortex heat exchanger to replace the traditional condenser under the framework of the single-stage compression system. High-temperature and high-pressure gas forms a high-speed vortex flow in the inner cavity of the subcritical flow vortex heat exchanger. Part of the high-temperature gas can approach the critical temperature and present a subcritical flow state, thereby directly achieving high-temperature hot water of 80℃ to 90℃ under the low pressure ratio of the single-stage compression system. Compared with the original single-stage compression system, the high-temperature hot water below 50℃ of the traditional condenser at low pressure ratio has a significantly stronger heating capacity.

[0018] (2) High-pressure and high-temperature gas enters the gas vortex flow zone horizontally through the air inlet nozzle to form a high-speed vortex flow. After entering the energy separation zone, the gas molecules in the inner layer transfer kinetic energy to the gas molecules in the outer layer, causing the gas molecules in the inner layer to lose kinetic energy, reduce the vibration frequency, and reduce the temperature, while the gas molecules in the outer layer gain kinetic energy, increase the vibration frequency, and increase the temperature, thereby generating radial energy transfer and separation along the central axis of the energy separation zone. The inner layer is a low-temperature zone, and part of the gas is condensed into a low-temperature and low-pressure vapor-liquid mixture and discharged from the cold-end vapor outlet; while the outer layer is a high-temperature zone, and part of the gas rotating at high speed close to the critical temperature will present a subcritical flow state. After transferring heat to the cooling water in the cooling water zone through the heat exchange core tube, the condensed low-temperature and high-pressure vapor-liquid mixture is then discharged from the hot-end vapor outlet; the structure is interconnected and the design is exquisite.

[0019] (3) The hot end gas outlet of the subcritical flow vortex heat exchanger is connected to the expansion valve. Because the low-temperature and high-pressure gas-liquid mixture condensed after heat transfer cannot directly enter the economizer, it needs to be decompressed separately and turned into a low-temperature and low-pressure gas-liquid mixture before it can merge with the low-temperature and low-pressure gas-liquid mixture at the cold end gas outlet. The design and layout are reasonable.

[0020] (4) The subcritical flow vortex heat exchanger is completely different from the existing condenser technology principle, structure and efficiency. It is a new type of thermal device designed and manufactured under the innovative technology concept. It increases the heat exchange temperature difference of the heat exchange core tube by generating a high temperature close to the critical point, thereby increasing the heat transfer capacity, achieving the effects of low pressure ratio, high temperature hot water and high heating energy efficiency ratio, and greatly improving the overall benefit and value of low temperature heat energy recovery.

[0021] (5) In the subcritical flow vortex heat exchanger, the air inlet nozzle extends horizontally and connects to the top of the exchanger shell, thereby ensuring that the high-temperature and high-pressure gas can enter horizontally at high speed. In the heat exchange core tube, the high-speed tangential wall flow will destroy the wall laminar flow that hinders heat transfer, making the airflow in a turbulent state, greatly improving the convective heat transfer coefficient between the airflow and the tube wall, and increasing the heat transfer capacity. Compared with the condenser of the existing single-stage compression system, the device volume is greatly reduced when the heat transferred is the same, and the heat transfer efficiency is high.

[0022] To sum up, it has the advantages of stronger heating capacity, low pressure ratio, high temperature hot water, high heating energy efficiency ratio, and reasonable design and layout. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the present invention.

[0024] Figure 2 This is the lgp-h diagram of a single-stage compression cycle with low-temperature potential heat recovery.

[0025] Figure 3This is a structural cross-sectional view of a subcritical flow vortex heat exchanger.

[0026] Figure 4 for Figure 1 Right view of .

[0027] Figure 5 Schematic diagram of a single-stage compression system.

[0028] Figure 6 Schematic diagram of a two-stage compression system. DETAILED DESCRIPTION

[0029] The present invention will be further described below by way of examples and in conjunction with the accompanying drawings:

[0030] Combine Figure 1 — Figure 6 As shown, a heat recovery circulation system with high heating energy efficiency consists of an economizer E, an expansion valve D connected to the front and rear sides of the economizer E, and an evaporator A, a compressor B, and a subcritical flow vortex heat exchanger C connected in sequence.

[0031] Evaporator A is used for the refrigerant gas to absorb heat at a low temperature so that the refrigerant gas is in a low-temperature and low-pressure gas state.

[0032] Compressor B is used to elevate the incoming low-temperature, low-pressure gas into high-temperature, high-pressure gas.

[0033] The subcritical flow vortex heat exchanger C consists of an exchanger shell 1, an air inlet nozzle 2 extending horizontally and connected to the top of the exchanger shell 1, a cold end gas outlet 3 centrally located at the front end of the exchanger shell 1, and a hot end gas outlet 4 centrally located at the rear end of the exchanger shell 1.

[0034] The cold end gas outlet 3 is directly connected to the economizer E.

[0035] The hot end gas outlet 4 is connected to the economizer E through the first expansion valve D, and the outlet of the second expansion valve D is connected to the evaporator A, thus forming a closed circuit;

[0036] The heat exchanger shell 1 is in the shape of a long tube as a whole, and a heat exchange core tube 11 is coaxially installed in the middle and rear part of the cavity.

[0037] The heat exchange core tube 11 divides the inner cavity of the exchanger shell 1 into an energy separation zone 5 and a cooling water zone 6 .

[0038] A cooling water inlet 61 and a cooling water outlet 62 are radially provided at the front and rear ends of the exchanger housing 1 corresponding to the cooling water area 6 .

[0039] The front cavity of the exchanger housing 1 is communicated with the air inlet nozzle 2 and serves as a gas vortex flow zone 7 for the high-speed tangentially entering high-pressure and high-temperature gas to form a high-speed vortex flow.

[0040] When the gas swirling into the energy separation zone 5 is separated into an inner layer of low-temperature gas and an outer layer of high-temperature gas under the action of a high-speed centrifugal vortex, the gas in the outer layer of high-temperature gas in a subcritical flow state transfers heat with the cooling water zone 6 with the help of the heat exchange core tube 11.

[0041] The inner wall of the heat exchange core tube 11 is spirally circumferentially provided with metal inner spiral fins 111, and the outer wall is spirally circumferentially provided with metal outer spiral fins 112, so that the gas in the subcritical flow state in the high-temperature and high-pressure gas can transfer heat with the cooling water area 6 with the help of the metal inner spiral fins 111 and the metal outer spiral fins 112.

[0042] The metal inner-spinning ribs 111 and the metal outer-spinning ribs 112 are both made of porous metal.

[0043] The outer ends of the metal outward-turning fins 112 are close to the inner wall of the exchanger housing 1 .

[0044] There is a distance between the metal inwardly spiral fin 111 and the inner end of the cold steam guide pipe 31 in both the axial and radial directions.

[0045] The hot end gas outlet 4 is used to extract the low temperature and high pressure gas-liquid mixed state G which is condensed after the heat transfer of the outer high temperature gas. H .

[0046] The cold end gas outlet 3 is used to export the low temperature and low pressure gas-liquid mixed state G which is condensed after the inner layer low temperature gas exchanges energy with the outer layer high temperature gas. C .

[0047] The cold end gas outlet 3 and the hot end gas outlet 4 are respectively centrally located at the front and rear ends of the exchanger housing 1 .

[0048] The cold end gas outlet 3 is provided with a cold gas guide pipe 31 extending axially from the front end of the exchanger housing 1 to the energy separation zone 5 .

[0049] A conical inward-facing microporous plate is provided at the rear end of the cold steam guide pipe 31 .

[0050] The transition section between the gas vortex flow area 7 and the heat exchange core tube 11 is provided with a tapered tube 8 connected from the inner wall of the exchanger shell 1 to the front end of the heat exchange core tube 11.

[0051] The reducer 8 is used to block the front end of the cooling water area 6 and guide the axial swirl flow of the gas in the gas vortex flow area 7 to the energy separation area 5.

[0052] The diameter of the hot end gas outlet 4 is between the inner diameter of the heat exchange core tube 11 and the diameter of the cold end gas outlet 3.

[0053] The specific implementation steps are as follows:

[0054] Step S1: The refrigerant gas is subjected to heat absorption at a low temperature by the evaporator A so that the refrigerant gas is in a low-temperature and low-pressure gas state, and the low-temperature and low-pressure gas is transferred into the compressor B to form a high-temperature and high-pressure gas.

[0055] Step S2: The high-temperature and high-pressure gas is discharged into the subcritical flow vortex heat exchanger C, and then the high-temperature and high-pressure gas is subjected to high-temperature heat release with the help of the subcritical flow vortex heat exchanger C. The high-temperature and high-pressure gas enters the inner cavity of the subcritical flow vortex heat exchanger C at a high speed and tangentially to form a high-speed vortex flow, and radial energy transfer and separation are generated under the action of the high-speed centrifugal vortex. The energy of the inner layer gas will be transferred to the outer layer gas, thereby forming an inner layer of low-temperature and low-pressure gas and an outer layer of high-temperature and high-pressure gas.

[0056] Step S3: low-temperature and low-pressure gas condensed into a low-temperature and low-pressure vapor-liquid mixed state G C The gas is discharged from the cold end gas outlet 3 of the subcritical flow vortex heat exchanger C to the economizer E. Part of the high-temperature and high-pressure gas is close to the critical temperature due to high-speed rotation, thus presenting a subcritical flow state, and heat is transferred in the inner cavity of the subcritical flow vortex heat exchanger C. Then, the low-temperature and high-pressure gas-liquid mixed state G after the heat transfer H The gas is discharged from the hot end gas outlet 4 of the subcritical flow vortex heat exchanger C to the expansion valve D for separate decompression, and the formed low-temperature and low-pressure gas-liquid mixture is then discharged into the economizer E.

[0057] In step S4, the low-temperature and low-pressure vapor-liquid mixture discharged into the economizer E is transferred to the next expansion valve D for collective decompression, and finally discharged back to the evaporator A. Steps S1-S4 are repeated to perform a new round of heating cycle.

Claims

1. A heat recovery circulation system with high heating energy efficiency, characterized by: The invention comprises an economizer (E), an expansion valve (D) connected to the front and rear sides of the economizer (E), and an evaporator (A), a compressor (B), and a subcritical flow vortex heat exchanger (C) connected in sequence. The subcritical flow vortex heat exchanger (C) comprises an exchanger shell (1), an air inlet nozzle (2) extending horizontally and connected to the top of the exchanger shell (1), a cold end gas outlet (3) centrally located at the front end of the exchanger shell (1), and a hot end gas outlet (4) centrally located at the rear end of the exchanger shell (1). The cold end gas outlet (3) is directly connected to the economizer (E), the hot end gas outlet (4) is connected to the economizer (E) through the front expansion valve (D), and the outlet of the rear expansion valve (D) is connected to the evaporator (A), thereby forming a closed loop. The exchanger shell (1) is in the shape of a long tube as a whole, and a heat exchange core tube (11) is coaxially installed in the middle and rear part of the cavity. The heat exchange core tube (11) divides the inner cavity of the exchanger shell (1) into energy exchange and heat exchange zones. The energy separation zone (5) and the cooling water zone (6) are connected. The front cavity of the exchanger shell (1) is connected with the air inlet nozzle (2) and serves as a gas vortex flow zone (7) for high-speed tangential high-pressure high-temperature gas to form a high-speed vortex flow. When the gas spiraling into the energy separation zone (5) is separated into an inner layer of low-temperature gas and an outer layer of high-temperature gas under the action of the high-speed centrifugal vortex, the gas in the outer layer of high-temperature gas in a subcritical flow state transfers heat with the cooling water zone (6) by means of a heat exchange core tube (11). The hot end gas outlet (4) is used to guide out the low-temperature high-pressure gas-liquid mixed state condensed after the heat transfer of the outer layer of high-temperature gas, and the cold end gas outlet (3) is used to guide out the low-temperature low-pressure gas-liquid mixed state condensed after the energy exchange of the inner layer of low-temperature gas with the outer layer of high-temperature gas; the cold end gas outlet (3) is provided with a cold steam guide pipe (31) extending axially from the front end of the exchanger shell (1) to the energy separation zone (5); the rear end of the cold steam guide pipe (31) is provided with a conical indented microporous plate.

2. The heat recovery circulation system with high heating energy efficiency according to claim 1, characterized in that: The transition section between the gas vortex flow zone (7) and the heat exchange core tube (11) is provided with a tapered tube (8) connected from the inner wall of the exchanger shell (1) to the front end of the heat exchange core tube (11), and the tapered tube (8) is used to seal the front end of the cooling water zone (6) and guide the axial rotation of the gas in the gas vortex flow zone (7) to the energy separation zone (5).

3. The heat recovery circulation system with high heating energy efficiency according to claim 1, characterized in that: The heat exchange core tube (11) is provided with metal inner spiral fins (111) on its inner wall in a spiral manner, and metal outer spiral fins (112) on its outer wall in a spiral manner, so that the gas in a subcritical flow state in the high-temperature and high-pressure gas can transfer heat with the cooling water area (6) by means of the metal inner spiral fins (111) and the metal outer spiral fins (112).

4. The high heating energy efficiency heat recovery circulation system according to claim 3 is characterized by: The metal inner-rotating ribs (111) and the metal outer-rotating ribs (112) are both made of porous metal.

5. The heat recovery circulation system with high heating energy efficiency according to claim 4, characterized in that: The outer end of the metal outward-turning fin (112) is close to the inner wall of the exchanger shell (1), and the metal inward-turning fin (111) is spaced apart from the inner end of the cold steam guide tube (31) in both the axial and radial directions.

6. The heat recovery circulation system with high heating energy efficiency according to claim 1, characterized in that: The exchanger housing (1) is radially provided with a cooling water inlet (61) and a cooling water outlet (62) at the front and rear ends corresponding to the cooling water area (6), respectively.

7. The heat recovery circulation system with high heating energy efficiency according to claim 1, characterized in that: The hot end gas outlet (4) has a diameter between the inner diameter of the heat exchange core tube (11) and the diameter of the cold end gas outlet (3).

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