A heat pump drying system with cold and hot heat exchanger pre-evaporator

Abstract

The present application relates to a kind of heat pump drying system with cold and hot confluence pre-evaporator in the field of drying device, the refrigerant outlet of main evaporator is connected compressor, condenser, expansion valve in turn, the hot air outlet of condenser is connected the air inlet of dryer, the air outlet of dryer is connected with pre-evaporator by dust removal device, the pre-evaporator includes vertically arranged cylinder, cylinder side is equipped with hot air inlet and cold air inlet, cylinder is equipped with side refrigerant coil and bottom refrigerant coil outside and is connected between expansion valve and compressor refrigerant inlet in series with main evaporator, cylinder top is equipped with air outlet and is connected with main evaporator air inlet, cylinder bottom is equipped with condensate outlet.The present application can fully recover the condensation heat of water vapor in waste heat airflow, and fine dust in dryer waste heat airflow can be discharged together with condensate water.The device can be used for drying of grain, fruits and vegetables, tea and other industrial materials.

Description

Technical Field

[0001] This invention relates to a heat pump drying device, and more particularly to a heat pump drying system for grains or other materials with waste heat recovery function. Background Technology

[0002] In existing technology, there is a heat pump grain drying system, which mainly includes a compressor. The refrigerant outlet of the compressor is connected to the refrigerant inlet of the condenser. The refrigerant outlet of the condenser is connected to the refrigerant inlet of the main evaporator via an expansion valve. The refrigerant outlet of the evaporator is connected to the compressor inlet. The hot air outlet after heat exchange in the condenser is connected to the dryer. The waste heat air from the dryer outlet is connected to the air inlet of the evaporator via a dust removal device. The airflow from the dryer outlet carries a large amount of waste heat that needs to be recovered. However, this large amount of waste heat airflow also carries steam generated during the drying process. This waste heat gas containing steam enters the evaporator of the heat pump device for recovery and utilization. The evaporator also needs to be supplemented with atmospheric air to obtain some energy from the atmosphere. Therefore, the evaporator has two air inlets: one for recovering waste heat and the other for supplementing energy from the atmosphere. Otherwise, the energy imbalance of the entire device will prevent the dryer from operating continuously and normally. In this way, the hot airflow carrying water vapor and the supplemented atmosphere, i.e., the cold airflow, converge. When the hot and cold airflows converge, a large amount of condensate will be generated at the evaporator inlet. The condensation heat is lost with the condensate before it can even contact the evaporator fins and cannot be utilized. Therefore, no one in the current technology uses such a simple method to replenish the atmosphere.

[0003] The existing technologies include the following methods: (1) Using dehydration measures to ensure that the waste heat gas flow does not carry water vapor before entering the evaporator, without utilizing the condensation heat of the steam in the waste heat gas flow. (2) Utilizing the condensation heat of the steam in the waste heat gas flow is achieved by setting up separate independent modules for condensation heat recovery and independent modules for atmospheric replenishment, which requires multiple heat pump systems with two or more compressors. (3) Not replenishing the atmosphere at all, using a fully closed loop.

[0004] The shortcomings are as follows: In the existing waste heat utilization method (1), the condensation heat of the steam contained in the waste heat gas flow is not utilized, and only the sensible heat of the dry hot air in the waste heat gas flow is utilized. According to calculations, the condensation heat of the steam contained in the waste heat gas flow is far greater than the sensible heat recovered by the waste heat gas flow using the temperature difference, which is a great waste. In the existing waste heat utilization method (2), the system is complex, requires more equipment, and the cost is greatly increased. In the existing waste heat utilization method (3), although the evaporator can utilize the sensible heat of the waste heat gas flow and the condensation heat of the steam contained therein, it is necessary to add auxiliary electric heating or a compressor with a certain power to maintain the thermal balance of the entire system, and the power consumption required for drying a unit weight of material will be too high. Summary of the Invention

[0005] The purpose of this invention is to provide a heat pump drying system with a pre-evaporator that integrates hot and cold airflow. This system requires only one compressor and one heat pump system. It not only utilizes the sensible heat of the waste heat airflow from the dryer outlet but also fully recovers the condensation heat of water vapor in the waste heat airflow, achieving full utilization of waste heat. Simultaneously, it can automatically clean the fine particulate dust in the waste heat airflow from the condensate formed by the hot and cold airflow integration. This simplifies the dust collectors used in existing technologies. For example, the bag filters and other fine filtration equipment used in existing grain drying systems or heat pump material drying systems can be omitted, requiring only the primary filtration equipment. This significantly reduces the heat dissipation area of ​​the dust collector, thereby reducing heat loss from the waste heat airflow, and also reduces the total investment in the system equipment and the required plant area. Since the presence of fine particulate dust in the atmosphere near the drying equipment is a common problem, this invention also allows the fine particulate dust in the supplementary atmosphere to be effectively removed in the pre-evaporator, avoiding the common problem in existing evaporators where fine particulate dust in the atmosphere causes dust accumulation on the evaporator fins, affecting efficiency.

[0006] Therefore, the technical solution of the present invention is: a heat pump drying system with a hot and cold confluence pre-evaporator, including an evaporator, the refrigerant outlet of the evaporator being connected to the refrigerant inlet of the compressor, the refrigerant outlet of the compressor being connected to the refrigerant inlet of the condenser, the refrigerant outlet of the condenser being connected to the inlet of the throttling device, the hot air outlet of the condenser being connected to the air inlet of the dryer, the air outlet of the dryer being connected to the air inlet of the dust removal device, and the air outlet of the dust removal device being connected in sequence to the pre-evaporator and the main evaporator. The pre-evaporator includes a vertically arranged cylinder, a hot air inlet connected to the air outlet of the dust removal device on one side of the cylinder, a cold air inlet on the other side of the cylinder, the cold air inlet being open to the atmosphere, a side refrigerant coil outside the cylinder, the side refrigerant coil being connected in series with the main evaporator coil and then connected between the throttling device and the refrigerant inlet of the compressor, an air outlet at the top of the cylinder, and a condensate outlet at the bottom of the cylinder.

[0007] Compared with the prior art of type (1), this invention not only recovers a large amount of condensation heat, but also simplifies the bag filter, greatly reducing heat loss from the equipment surface, and the power consumption required for drying a unit weight of material will be reduced by more than 60%; compared with the prior art of type (2), this invention reduces the number of compressors and total power required, increases the COP value of the entire system, and reduces the power consumption required for drying a unit weight of material by 20%; compared with the prior art of type (3), this invention increases the COP value of the system due to the supplementary absorption of atmospheric energy, reduces the required compressor power, and also reduces equipment costs, and reduces the power consumption required for drying a unit weight of material by more than 40%. The main improvement of this invention is that it provides an evaporator that is different from the traditional one. This invention calls it a "pre-evaporator". The pre-evaporator can play part of the role of the evaporator, but does not independently undertake all the role of the evaporator. It is set before the traditional evaporator and used in series with the traditional evaporator. The traditional evaporator in this invention is actually the "main evaporator". The pre-evaporator cylinder has a hot air inlet on one side connected to the air outlet of the dust removal device, and a cold air inlet on the other side. After the humid and hot air dried by the dryer mixes with the replenished atmosphere, the temperature drops below the dew point, and the humidity in the air is saturated. Some of these saturated vapors in the waste heat gas flow condense into water droplets with dust as nuclei and fall down, while most of them come into contact with the lower-temperature side wall of the pre-evaporator cylinder. Their condensation heat is absorbed by the refrigerant in the side refrigerant coil, so that the condensation heat of the water vapor in the waste heat gas flow is fully recovered and utilized. After the refrigerant in the pre-evaporator absorbs the condensation heat, it further absorbs the sensible heat of the dry gas after the waste heat gas flow and the atmosphere are mixed in the main evaporator. Then, it is compressed by the compressor to provide the refrigerant in the condenser with a higher temperature and higher pressure to convert it into dry hot air for use in dryers for grains or other materials.

[0008] The specific operation of the pre-evaporator during the above-mentioned process is as follows: Because a refrigerant coil is installed on the side of the pre-evaporator cylinder, the heat absorption effect of refrigerant evaporation keeps the side wall temperature of the pre-evaporator very low. Most of the cold and hot airflows are thrown towards the low-temperature inner wall of the cylinder with great centrifugal force, producing condensation. The airflow after the cold and hot airflows converge is also thrown towards the low-temperature inner wall of the cylinder with great centrifugal force, producing condensation. The heat of condensation is absorbed by the refrigerant. All the condensate, along with dust particles, flows downwards along the side wall and is finally discharged from the bottom of the cylinder. A small portion of the airflow after the cold and hot airflows converges is located in the space inside the cylinder side wall. Here, the dust particles in the airflow act as nuclei, causing water droplets to condense on the surface of each dust particle when the cold and hot airflows converge, falling downwards. Therefore, the pre-evaporator also has a dust removal function, allowing the use of bag filters and other fine filtration equipment in the system to be omitted, retaining only the primary filtration equipment, reducing the total investment in the system equipment and the required plant area. This device can be mainly used in grain heat pump drying systems with waste heat utilization, and can also be used in heat pump drying systems for various powdery materials, as well as in drying systems for fruits, vegetables, tea, tobacco and other materials.

[0009] Furthermore, the hot air inlet and the cold air inlet are tangentially connected to the outside of the cylindrical body. The hot air inlet and the cold air inlet can also be arranged symmetrically at the center. The tangential entry of the hot air inlet and the cold air inlet into the cylinder creates a swirling flow, causing most of the condensed water to move towards the inner wall of the cylinder, thus allowing the side refrigerant coil to absorb heat more fully.

[0010] To prevent heat loss, the cylinder is provided with an outer shell, and an insulation layer is provided between the outer shell and the cylinder.

[0011] Furthermore, the bottom of the cylinder is conical or concave, and a bottom condensate coil is provided outside the conical or concave shell. The condensate outlet is located at the very bottom of the conical or concave shell, and the bottom condensate coil is connected in series with the side condensate coil. The bottom condensate coil allows the condensate at the bottom of the cylinder to further absorb the heat it contains before being discharged, ensuring more complete waste heat recovery.

[0012] To further enhance the heat transfer effect, the refrigerant coil on the side of the cylinder is bent up and down and welded to the outer wall of the cylinder, and the refrigerant coil at the bottom is welded to the outer wall of the bottom of the cylinder.

[0013] Furthermore, a circular baffle is provided at the center of the upper part of the cylinder, and the baffle is connected to the inner wall of the cylinder via a support member. Under the action of the baffle, the airflow runs upward from the side of the cylinder, thereby improving the evaporation and heat absorption of the side refrigerant coil. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of the present invention.

[0015] Figure 2 This is a schematic diagram of the pre-evaporator structure.

[0016] Figure 3 This is a schematic diagram of the three-dimensional structure of the pre-evaporator after the insulation layer has been removed.

[0017] Figure 4 This is the structure after a partial cut-open section of the pre-evaporator.

[0018] In the diagram, 1 is the cold air inlet, 2 is the side refrigerant coil, 3 is the hot air inlet, 4 is the insulation layer, 5 is the cylinder, 6 is the outer shell, 7 is the air outlet, 8 is the condensate outlet, 9 is the bottom refrigerant coil, 10 is the compressor, 11 is the condenser, 12 is the dryer, 13 is the expansion valve, 14 is the main evaporator, 15 is the dust removal device, 16 is the baffle, and 17 is the support component. Detailed Implementation

[0019] like Figure 1-4 As shown, a heat pump drying system with a hot and cold combustor pre-evaporator is provided. It includes a main evaporator 14, whose refrigerant outlet is connected to the refrigerant inlet of a compressor 10. The refrigerant outlet of the compressor 10 is connected to the refrigerant inlet of a condenser 11, and the refrigerant outlet of the condenser 11 is connected to the inlet of an expansion valve 13. The hot air outlet of the condenser 11 is connected to the air inlet of a dryer 12, and the air outlet 7 of the dryer 12 is connected to the air inlet of a dust removal device 15. The air outlet 7 of the dust removal device 15 is connected to the pre-evaporator. The pre-evaporator includes a vertically arranged cylinder 5. One side of the cylinder 5 has a hot air inlet 3 connected to the air outlet 7 of the dust removal device 15, and the other side of the cylinder 5 has a cold air inlet 1. A side refrigerant coil 2 is provided outside the cylinder 5. The side refrigerant coil 2 is connected in series with the main evaporator 14 between the expansion valve 13 and the refrigerant inlet of the compressor 10. The top of the cylinder 5 has an air outlet 7, and the bottom of the cylinder 5 has a condensate outlet 8.

[0020] Furthermore, the hot air inlet 3 and the cold air inlet 1 are tangentially connected to the outside of the cylindrical body 5. The hot air inlet 3 and the cold air inlet 1 can also be arranged symmetrically at the center. The tangential entry of the hot air inlet 3 and the cold air inlet 1 into the cylindrical body 5 creates a swirling flow, causing the condensed water to move towards the inner wall of the cylindrical body 5, thus allowing the side refrigerant coil 2 to absorb heat more fully.

[0021] To avoid heat loss, the cylinder 5 is provided with an outer shell 6, and an insulation layer 4 is provided between the outer shell 6 and the cylinder 5.

[0022] Furthermore, the bottom of the cylinder 5 is conical or concave, and a bottom refrigerant coil 9 is provided outside the conical or concave shape. The condensate outlet 8 is located at the very bottom of the conical or concave shape, and the bottom refrigerant coil 9 is connected in series with the side refrigerant coil 2. The bottom refrigerant coil 9 can further absorb the heat in the condensate, ensuring more complete waste heat recovery.

[0023] To further enhance the heat transfer effect, the side refrigerant coil 2 is bent up and down and welded to the outer wall of the cylinder 5, and the bottom refrigerant coil 9 is welded to the bottom outer wall of the cylinder 5.

[0024] A circular baffle 16 is provided at the center of the upper part of the cylinder 5, and the baffle 16 is connected to the inner wall of the cylinder 5 via a support member 17. Under the action of the baffle 16, the airflow runs upward from the side of the cylinder, thereby improving the evaporation and heat absorption of the side refrigerant coil.

[0025] Figure 1 The middle arrow indicates the airflow direction. The bottom refrigerant coil 9 and the side refrigerant coil 2 are connected in series with the main evaporator 14, so that the pre-evaporator can play part of the function of the evaporator, but does not independently undertake the entire function of the evaporator. By supplementing some cold air into the cylinder 5, the temperature of the dried humid air is reduced to below the dew point, and the humidity in the air is saturated. The refrigerant evaporates and absorbs heat in the pre-evaporator, which can further reduce the temperature of the hot air and allow the latent heat of vaporization in the air to be fully released. After absorbing the condensation heat, the refrigerant in the pre-evaporator evaporates further in the main evaporator 14, and comes into further contact with the supplemented air from the outside, absorbing heat from the air. The heat is then converted into dry hot air by the compressor 10 and the condenser 11 for use by the dryer 12. During the above operation, hot and cold air enter from the periphery of the cylinder 5 and then flow upwards. Condensate condenses on the inner wall of the cylinder 5 and flows downwards. During the flow, it fully exchanges heat with the side refrigerant coil 2. Therefore, the pre-evaporator can fully recover the heat in the air and the condensation heat of the condensate, achieving the purpose of efficient reuse of waste heat.

[0026] Furthermore, dust in the air flows downwards with the condensate, and the smooth inner wall of cylinder 5 prevents dust accumulation. The dust is discharged from the bottom along with the condensate, achieving self-cleaning of the pre-evaporator. This eliminates the need to introduce dust-laden hot air into the main evaporator 14 for waste heat recovery, reducing the possibility of blockage in the main evaporator 14 and making the device more reliable. This device can be used for drying various materials containing dust.

[0027] This invention is not limited to the above embodiments. Based on the technical solutions disclosed in this invention, those skilled in the art can make some substitutions and modifications to some of the technical features without creative effort, and all such substitutions and modifications are within the protection scope of this invention.

Claims

1. A heat pump drying system with a hot and cold combustor pre-evaporator, comprising an evaporator, wherein the refrigerant outlet of the evaporator is connected to the refrigerant inlet of a compressor, the refrigerant outlet of the compressor is connected to the refrigerant inlet of a condenser, the refrigerant outlet of the condenser is connected to the inlet of a throttling device, the hot air outlet of the condenser is connected to the air inlet of a dryer, and the air outlet of the dryer is connected to the air inlet of a dust removal device, characterized in that: The dust removal device's air outlet is sequentially connected to the pre-evaporator and the main evaporator. The pre-evaporator includes a vertically arranged cylindrical body. One side of the cylindrical body has a hot air inlet connected to the dust removal device's air outlet, and the other side has a cold air inlet open to the atmosphere. A side refrigerant coil is located outside the cylindrical body, and the side refrigerant coil is connected in series with the main evaporator between the throttling device and the compressor refrigerant inlet. The top of the cylindrical body has an air outlet, and the bottom of the cylindrical body has a condensate outlet. The hot air inlet and the cold air inlet are tangentially connected to the outside of the circular cylindrical body. The hot air inlet and the cold air inlet are centrally symmetrically arranged.

2. A heat pump drying system with a cold and hot manifold pre-evaporator according to claim 1, characterized in that: The cylinder is provided with an outer shell, and an insulation layer is provided between the outer shell and the cylinder.

3. A heat pump drying system with a hot and cold manifold pre-evaporator according to claim 1, characterized in that: The bottom of the cylinder is conical or concave, and a bottom refrigerant coil is provided outside the conical or concave shape. The condensate outlet is located at the bottom of the conical or concave shape, and the bottom refrigerant coil is connected in series with the side refrigerant coil.

4. A heat pump drying system with a hot and cold manifold pre-evaporator according to claim 3, characterized in that: The side refrigerant coil is bent up and down and welded to the outer wall of the cylinder, and the bottom refrigerant coil is welded to the bottom outer wall of the cylinder.

5. A heat pump drying system with a hot and cold manifold pre-evaporator according to claim 1, characterized in that: A circular baffle is provided at the center of the upper part of the cylinder, and the baffle is connected to the inner wall of the cylinder by a support member.

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