CN101216245A - heat pump dryer - Google Patents

Abstract

The invention discloses a heat pump dryer using high-efficiency and environment-friendly _CO2 as a working medium. The high-pressure end of the compressor is connected in series with the working medium side of two air source gas coolers and then connected to the internal heat exchanger. The high-pressure working medium side of the internal heat exchanger passes through the electronic expansion valve and the evaporator and then connects The low-pressure working medium side is connected to the low-pressure end of the compressor to form a working medium circulation system. The air side of the evaporator is connected in series with the second air source gas cooler and then connected to the inlet of the first stage drying chamber, and the outlet of the first stage drying chamber is connected in series with the first air source gas cooler and then connected to the second stage The inlet of the drying chamber and the outlet of the second-stage drying chamber are connected in series with the external heat exchanger and then connected to the inlet of the air side of the evaporator to form an air circulation system. The feature of the present invention is to design two-stage drying by using the heat exchange characteristics of the CO ₂ working medium heat pump, which reduces the temperature of the working medium at the outlet of the gas cooler, makes reasonable use of energy, and at the same time makes the drying run continuously and shortens the drying time.

Description

heat pump dryer

technical field

The invention belongs to drying equipment, in particular to a device for drying by means of a heat pump.

Background technique

Heat pump drying equipment has developed rapidly due to its characteristics of being closed, clean, high utilization rate of primary energy, high heating temperature, and easy capacity adjustment. However, the current application of the heat pump dryer system is a conventional working medium. The working fluids commonly used in the refrigeration heat pump industry are CFCs (chlorofluorocarbons) and HCFCs (hydrochlorofluorocarbons). Because of their damaging effects on the ozone layer and their greenhouse effect, scientists around the world are focusing on their alternatives. Among them, carbon dioxide has been reintroduced into the refrigeration heat pump industry due to its excellent environmental protection characteristics, good heat transfer and flow properties. At present, the natural working medium CO ₂ is known as one of the most potential alternative working fluids. According to the characteristics of the natural working medium CO ₂ heat pump, this scheme designs a CO ₂ heat pump two-stage dryer, which can also be applied to the R410A working medium system to improve the efficiency of the system while meeting the system requirements.

Contents of the invention

The object of the present invention is to provide a heat pump dryer using carbon dioxide and R410A as circulating working fluids.

The system flow of the present invention will be described below in conjunction with accompanying drawing 1 . The present invention includes compressor 1, air source gas cooler 2, internal heat exchanger 3, electronic expansion valve 4, evaporator 5, external heat exchanger 6, drying chamber 7, conveyor belt 8 and motor 9, etc. The circulating working fluid of the heat pump dryer is carbon dioxide, and R410A can also be used. The circulating refrigerant R410A is composed of difluoromethane (HFC-32, molecular formula CH ₂ F ₂ ) and pentafluoroethane (HFC-125, molecular formula CHF ₂ CF ₃ ), and the mass percentage of HFC-32/HFC-125 is 50/ 50%. The specific connection scheme of the system: the high-pressure end of compressor 1 is connected to the inlet of the working medium side of the first air source gas cooler 2-1, and the outlet of the working medium side of the air source gas cooler 2-1 is connected to the second air source The inlet of gas cooler 2-2 working medium side, the outlet of air source gas cooler 2-2 working medium side is connected to the inlet of high-pressure working medium side of internal heat exchanger 3, and the outlet of internal heat exchanger 3 high-pressure working medium side The electronic expansion valve 4 is connected to the working medium side of the evaporator 5, and the working medium side of the evaporator 5 is connected in series with the low-pressure working medium side of the internal heat exchanger 3 and then connected to the low-pressure end of the compressor 1 to form a working medium circulation system. The outlet of the air side of the evaporator 5 is connected in series with the air side of the second air source gas cooler 2-2 and then connected to the inlet of the first-stage drying chamber 7-1, and the outlet of the first-stage drying chamber 7-1 is connected to the first The air side of the air source gas cooler 2-1 is connected in series to the inlet of the second-stage drying chamber 7-2, and the outlet of the second-stage drying chamber 7-2 is connected in series to the air side of the external heat exchanger 6 and then connected to the The air side inlet of the evaporator 5 constitutes an air circulation system. The first stage drying chamber 7-1 is separated from the second stage drying chamber 7-2 with a soft curtain. The two drying chambers are provided with the same conveyor belt 8 driven by a motor 9 .

After the compressor 1 is turned on, the working medium is compressed by the compressor 1 into a high-temperature and high-pressure working medium and enters the air source gas cooler 2-1 to heat the air, and then enters the air source gas cooler 2-2 for further cooling after heat exchange. The working medium enters the internal heat exchanger 3 to exchange heat with the low-temperature and low-pressure working medium. The cooled working medium enters the electronic expansion valve 4 to throttle and reduce pressure. The low-temperature and low-pressure working medium enters the evaporator 5 for evaporation and heat exchange. The low-temperature and low-pressure working medium enters the interior The heat exchanger 3 is overheated, and the overheated low-temperature and low-pressure working fluid enters the compressor 1 to be compressed to complete a cycle.

While the carbon dioxide working medium is running, the air enters the evaporator 5 for cooling and dehumidification, enters the air source gas cooler 2-2 for the first heating and temperature rise, enters the drying chamber 7-1 for moisture absorption and drying, and then enters the air source gas cooler 2- 1 is heated for the second time, and then the drying chamber 7-2 performs moisture absorption and drying. After drying, it enters the external heat exchanger 6 to exchange heat with the external air, and then enters the evaporator 5 to cool down and dehumidify, completing a cycle.

The feature of the present invention is that two air source gas coolers are provided, so that the temperature of the working medium is lowered twice, and the air is heated twice, and the temperature is continuously raised. Such a design reduces the heat transfer temperature difference of the heat exchanger and improves the drying efficiency of the heat pump.

Description of drawings

Accompanying drawing is the system flow of the present invention and the connection diagram of each component.

Detailed ways

Below with Chinese cabbage seed drying as specific embodiment, content of the present invention is further described:

The dried material cabbage seeds are placed on the conveyor belt in the drying chamber. The initial moisture content of the cabbage seeds is 30%, and they are dried and dehydrated to a moisture content of 5%.

After the compressor 1 is turned on, the CO ₂ working medium is compressed by the compressor 1 into a high-temperature and high-pressure working medium with a pressure of 9MPa, and after the temperature is 75°C, it enters the air source gas cooler 2-1 for the first cooling down to 45°C; at the same time, the temperature is reduced to 45°C The air at 30°C and humidity of 80% is heated to 45°C and the _humidity drops to 35%. 25°C, while heating the air at 20°C and 100% humidity to 35°C and dropping the humidity to 55%. At this time, the CO ₂ working fluid enters the internal heat exchanger 3 to exchange heat with the low-temperature and low-pressure working fluid, and the cooled CO ₂ working fluid enters the electronic expansion valve 4 to reduce the pressure to 5MPa and the temperature is 15°C. The low-temperature and low-pressure CO ₂ working fluid enters the evaporator 5 for evaporation and heat exchange, and then enters the internal heat exchanger 3 to be overheated, and the temperature of the working fluid is raised to 25°C. The superheated low-temperature and low-pressure working medium enters the compressor 1 for compression to complete a cycle. While the carbon dioxide working medium is running, the air enters the evaporator 5 for cooling and dehumidification. The low-temperature and high-humidity air with a temperature of 20°C and a humidity of 100% enters the air source gas cooler 2-2 for the first heating, so that the temperature rises to 35°C and the relative humidity drops to 55%, and then enters the drying chamber 7-1 Moisture dry the seeds. At this time, the air temperature drops to 30°C, and the relative humidity increases to 80%, then the air enters the air source gas cooler 2-1 for the second heating, and the air temperature further increases to 45°C, and the relative humidity decreases to 35%. %, and then enter the drying chamber 7-2 to carry out moisture absorption drying to the seeds. The air after drying is 33°C and the humidity is 80%. The air enters the external heat exchanger 6 to exchange heat with the external air to cool down. After heat exchange, it enters the evaporator 5 to cool down and dehumidify. a cycle. The drying chamber 7-1 is separated from the drying chamber 7-2 by a soft curtain, and the cabbage seeds are dried in the high-temperature drying chamber 7-2 and the medium-temperature drying chamber 7-1 respectively, and the motor drives the drying chamber 7-1 and the drying chamber 7-1. The conveyor belt in chamber 7-2 moves slowly. The initial water content of the cabbage seeds is 30%, and they are dried in the medium temperature drying room 7-1. When the water content of the cabbage seeds reaches 12%, they enter the high temperature drying room 7-2 and continue to dry until the water content reaches 5%.

The advantages and beneficial effects of the present invention are that the system uses natural working fluid _CO2 as the working medium. In terms of system design, two air source gas coolers with different high and low temperatures are installed in the high temperature heat release part of the whole system and correspond to two high and low temperature coolers respectively. Drying chambers with different low temperatures are beneficial to reduce the temperature of the working fluid at the outlet of the system gas cooler, so that the energy can be used reasonably and the efficiency of the system can be improved. At the same time, the dry matter is continuously dried at two temperatures at the same time, which can reduce drying time. The invention has the characteristics of simple structure and convenient adjustment. It plays a positive role in promoting the popularization and application of CO ₂ working medium in heat pump drying system and energy saving.

Claims (4)

1. Heat pump dryer with compressor (1), air source gas cooler (2), internal heat exchanger (3), electronic expansion valve (4), evaporator (5), external heat exchanger (6) , drying chamber (7), conveyer belt (8) and motor (9), it is characterized in that compressor (1) high pressure terminal is connected to the inlet of first air source gas cooler (2-1) working medium side, described The outlet on the working medium side of the air source gas cooler (2-1) is connected to the inlet on the working medium side of the second air source gas cooler (2-2), and the working medium of the air source gas cooler (2-2) The outlet on the side of the internal heat exchanger (3) is connected to the high-pressure working medium side inlet of the internal heat exchanger (3), and the outlet on the high-pressure working medium side of the internal heat exchanger (3) is connected to the working medium of the evaporator (5) through the electronic expansion valve (4) side, the working medium side of the evaporator (5) is connected in series with the low-pressure working medium side of the internal heat exchanger (3) and then connected to the low-pressure end of the compressor (1) to form a working medium circulation system; the evaporator ( 5) The outlet of the air side is connected in series with the air side of the second air source gas cooler (2-2) and then connected to the inlet of the first-stage drying chamber (7-1), and the first-stage drying chamber (7-1) -1) the outlet is connected in series with the air side of the first air source gas cooler (2-1) and then connected to the inlet of the second-stage drying chamber (7-2), and the second-stage drying chamber (7-2) The outlet of -2) is connected in series with the air side of the external heat exchanger (6) and then connected to the air side inlet of the evaporator (5) to form an air circulation system. 2. The heat pump dryer according to claim 1, characterized in that the first-stage drying chamber (7-1) is separated from the second-stage drying chamber (7-2) by a soft curtain, and the two drying chambers The chamber is provided with the same conveyor belt (8) driven by a motor (9). 3. The heat pump dryer according to claim 1, characterized in that the heat pump circulating working fluid is carbon dioxide, and R410A can also be used as the circulating working fluid of the heat pump drying device. 4. The heat pump dryer according to claim 3, characterized in that the circulating working medium R410A is composed of difluoromethane (HFC-32) and pentafluoroethane (HFC-125), HFC-32/HFC- The mass percentage of 125 is 50/50%.

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