Fresh air heating system for preventing frost crack of fresh air coil pipe in low-temperature area

Abstract

The utility model discloses a fresh air heating system capable of preventing a fresh air coil pipe in a low-temperature area from frost cracking. The system comprises a fresh air heating coil, a plate heat exchanger, a hot water circulation loop A and a hot water circulation loop B, the hot water circulation loop A and the fresh air heating coil form a closed loop, the water outlet end of the fresh air heating coil is connected with one end of a water inlet pipe of the hot water circulation loop A, and the other end of the water inlet pipe of the hot water circulation loop A is connected with a water inlet A of the plate heat exchanger through a flexible connector and a pipeline connection reducer. The fresh air heating coil can be arranged at an inlet of the combined air handling unit or at a fresh air taking position of other modes, is in direct contact with outdoor low-temperature fresh air and is used for heating the fresh air and protecting the air handling coil and the like at the rear end from the risk of frost cracking. The plate heat exchanger is placed in a building and used for transferring heat between the two hot water circulation loops, the plate heat exchanger does not make direct contact with outdoor low-temperature fresh air, the plate heat exchanger is placed in a machine room without the frost crack risk, and the frost crack risk is avoided from the source.

Description

Technical Field

[0001] The utility model relates to the field of fresh air heating systems, and more specifically to a fresh air heating system for preventing the fresh air coil from cracking in low-temperature regions. Background Art

[0002] In Northeast and Northwest China, the winter temperature is very low, and the fresh air air-conditioning system is prone to cracking the coil. The main reason for the cracking of the fresh air preheating coil is that the water temperature in the coil drops below 0°C, and the volume increases after freezing, causing cracking. The heat exchanger coil is generally set with multiple internal passages. For an ideal heat exchanger, the lengths, resistances, and heat transfer uniformity of the internal passages should be the same. In actual manufacturing, limited by factors such as the design level of different manufacturers, the number of coil rows, and dimensions, when the inlet water temperature of each passage is the same, it is very difficult to keep the outlet water temperature and outlet water flow of each passage consistent. Therefore, there is often a situation where even though the supply and return water temperatures are significantly above the freezing point, the coil still cracks. This situation generally occurs in the passages with long internal pipelines, small water flow, and large heat transfer capacity in the heat exchanger.

[0003] The air-side temperature control of traditional fresh air heat exchange coils is achieved by adjusting the opening of the electric control valve on the hot water return pipe. When the opening of the electric control valve changes, the water flow rate in the coil also changes. When the water flow rate slows down, the coil is very prone to cracking. After the coil cracks, it not only causes equipment damage, but also affects the normal temperature, humidity, and pressure control of the air-conditioned area served by this air-conditioning equipment. Seriously, it may lead to the suspension of production in the factory.

[0004] In engineering, ethylene glycol solution is often used instead of aqueous solution to prevent freezing by using the lower freezing point of ethylene glycol. However, the ethylene glycol system has a certain corrosive effect on pipelines and coils. Moreover, after using ethylene glycol, the heat transfer effect of the heat exchange coil is significantly reduced, and the heating effect on fresh air becomes worse. And ethylene glycol is also a harmful substance to the human body, and there is also a pollution risk after leakage.

[0005] In engineering, fresh air heating coils without control valves are also often used to increase the water flow rate in the heating coil to prevent freezing. Increasing the water flow rate is an effective anti-freezing measure, but this method cannot solve the problem of fresh air temperature control. Therefore, a fresh air heating system with high heat transfer efficiency, safety, stability, and very good temperature control function is very necessary. Summary of the Utility Model

[0006] Therefore, to solve the above deficiencies, the utility model provides a fresh air heating system for preventing the fresh air coil from cracking in low-temperature regions.

[0007] The present utility model is realized as follows. A fresh air heating system for preventing the fresh air coil from cracking in low-temperature regions is constructed, and is characterized in that the system includes one fresh air heating coil, one plate heat exchanger, hot water circulation loop A and hot water circulation loop B. The hot water circulation loop A and the fresh air heating coil form a closed loop. The water outlet end of the fresh air heating coil is connected to one end of the water inlet pipe of the hot water circulation loop A. The other end of the water inlet pipe of the hot water circulation loop A is connected to the water inlet A of the plate heat exchanger through a flexible connection, a pipe and a reducer. The water outlet A of the plate heat exchanger is connected to one end of the water outlet pipe of the hot water circulation loop A. A circulation pump is provided on the water outlet pipe of the hot water circulation loop A. The other end of the water outlet pipe of the hot water circulation loop A is connected to the water inlet of the fresh air heating coil. One end of the water inlet pipe of the hot water circulation loop B is connected to the main building hot water supply pipe, and the other end of the water supply pipe of the hot water circulation loop B is connected to the water inlet B of the plate heat exchanger.

[0008] Furthermore, on the water supply pipe of the hot water circulation loop B, a butterfly valve, a pressure gauge, a filter, a pressure gauge, a butterfly valve, a flexible connection, and a pipe and a reducer are sequentially connected, and the pipe and the reducer are on the side close to the plate heat exchanger.

[0009] Furthermore, the water outlet of the plate heat exchanger is connected to one end of the return water pipe of the hot water circulation loop B. The other end of the return water pipe of the hot water circulation loop B is connected to the main building hot water return pipe. An electric control valve is provided on the return water pipe of the hot water circulation loop B. By adjusting the opening of this electric control valve, the water flow rate of the hot water circulation system B is controlled, and thus the water temperature of the hot water circulation system A is controlled, so as to control the temperature of the fresh air after passing through the fresh air heating coil.

[0010] Furthermore, in the hot water circulation loop A, between the fresh air heating coil and the plate heat exchanger, forced circulation is carried out by a circulation pump. There are two circulation pumps, and the two pumps are arranged in parallel. The two pumps work simultaneously to avoid the situation that the hot water stops flowing due to pump failure. The pumps adopt fixed-frequency pumps, and the water volume is constant, avoiding the situation that the water flow rate decreases due to the decrease of the pump frequency.

[0011] Furthermore, the fresh air heating coil can be arranged at the entrance of the modular air handling unit or at other fresh air intake points, in direct contact with the outdoor low-temperature fresh air, for heating the fresh air and protecting the air handling coils at the rear end from the risk of cracking. The plate heat exchanger is placed inside the building, used for transferring heat between the two hot water circulation loops. The plate heat exchanger is not in direct contact with the outdoor low-temperature fresh air and is placed in a machine room without the risk of cracking, avoiding the risk of cracking from the source.

[0012] The utility model has the following advantages: The utility model provides a fresh air heating system for preventing the fresh air coil in low-temperature areas from freezing and cracking; the advantages are as follows: The hot water circulation loop A and the fresh air heating coil form a closed loop. The water outlet end of the fresh air heating coil is connected to one end of the water inlet pipe of the hot water circulation loop A. The other end of the water inlet pipe of the hot water circulation loop A is connected to the water inlet A of the plate heat exchanger through a flexible connection, a pipe, and a reducing pipe. The water outlet A of the plate heat exchanger is connected to one end of the water outlet pipe of the hot water circulation loop A. A circulation pump is provided on the water outlet pipe of the hot water circulation loop A. The other end of the water outlet pipe of the hot water circulation loop A is connected to the water inlet of the fresh air heating coil. One end of the water inlet pipe of the hot water circulation loop B is connected to the main building hot water supply pipe. The other end of the water supply pipe of the hot water circulation loop B is connected to the water inlet B of the plate heat exchanger. A butterfly valve, a pressure gauge, a filter, a pressure gauge, a butterfly valve, a flexible connection, and a reducing pipe are sequentially connected to the water supply pipe of the hot water circulation loop B, and the reducing pipe is close to the side of the plate heat exchanger. The water outlet of the plate heat exchanger is connected to one end of the return water pipe of the hot water circulation loop B. The other end of the return water pipe of the hot water circulation loop B is connected to the main building hot water return pipe. An electric control valve is provided on the return water pipe of the hot water circulation loop B. By adjusting the opening degree of this electric control valve, the water flow rate of the hot water circulation system B is controlled, and then the water temperature of the hot water circulation system A is controlled, so as to control the temperature of the fresh air after passing through the fresh air heating coil. The hot water in the hot water circulation loop A is forced to circulate between the fresh air heating coil and the plate heat exchanger by a circulation pump. There are two circulation pumps, and the two pumps are connected in parallel. The two pumps work simultaneously to avoid the situation where the hot water stops flowing due to pump failure. The pump adopts a fixed-frequency pump, and the water volume is constant, avoiding the situation where the water flow rate decreases due to the decrease of the pump frequency. The fresh air heating coil can be set at the entrance of the modular air handling unit or other fresh air intake points, directly contacting the outdoor low-temperature fresh air, used to heat the fresh air, and protecting the air handling coil at the back end from the risk of freezing and cracking. The plate heat exchanger is placed inside the building, used to transfer heat between the two hot water circulation loops. The plate heat exchanger does not directly contact the outdoor low-temperature fresh air and is placed in a machine room without the risk of freezing and cracking, avoiding the risk of freezing and cracking from the source. By adding the hot water circulation loop A, the hot water flow rate of the fresh air heating coil is ensured to be stable and sufficient, and it will not freeze and crack due to the fluctuation and decrease of the hot water flow rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a schematic diagram of the implementation of the fresh air heating system of the present application.

[0014] Wherein: butterfly valve 1, reducing pipe 2, flexible connection 3, filter 4, check valve 5, electric control valve 6, pressure gauge 7. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0015] The following will be combined with the attached Figure 1A detailed description of the present utility model is given, and the technical solutions in the embodiments of the present utility model are described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative work belong to the protection scope of the present utility model.

[0016] The present utility model provides a fresh air heating system for preventing a fresh air coil from freezing by improvement. This system includes 1 fresh air heating coil, 1 plate heat exchanger, hot water circulation loop A and hot water circulation loop B.

[0017] During implementation; hot water circulation loop A includes: a water supply pipe, a return pipe, a pipe connection reducer, a flexible connection, a butterfly valve, a check valve, a pressure gauge, a water pump, and a filter. Hot water circulation loop B includes: a water supply pipe, a return pipe, a pipe connection reducer, a flexible connection, a butterfly valve, a pressure gauge, an electric control valve, and a filter.

[0018] During implementation; hot water circulation loop A and the fresh air heating coil form a closed loop. The water outlet end of the fresh air heating coil is connected to one end of the water inlet pipe of hot water circulation loop A. The other end of the water inlet pipe of hot water circulation loop A is connected to the water inlet A of the plate heat exchanger through a flexible connection and a pipe connection reducer. The water outlet A of the plate heat exchanger is connected to one end of the water outlet pipe of hot water circulation loop A. A circulation water pump is provided on the water outlet pipe of hot water circulation loop A. The other end of the water outlet pipe of hot water circulation loop A is connected to the water inlet of the fresh air heating coil. One end of the water inlet pipe of hot water circulation loop B is connected to the main building hot water supply pipe. The other end of the water supply pipe of hot water circulation loop B is connected to the water inlet B of the plate heat exchanger. A butterfly valve, a pressure gauge, a filter, a pressure gauge, a butterfly valve, a flexible connection, and a pipe connection reducer are sequentially connected to the water supply pipe of hot water circulation loop B, and the pipe connection reducer is on the side close to the plate heat exchanger; the water outlet of the plate heat exchanger is connected to one end of the return pipe of hot water circulation loop B. The other end of the return pipe of hot water circulation loop B is connected to the main building hot water return pipe. An electric control valve is provided on the return pipe of hot water circulation loop B. By adjusting the opening of this electric control valve, the water flow of hot water circulation system B is controlled, and then the water temperature of hot water circulation system A is controlled, so as to control the temperature of the fresh air after passing through the fresh air heating coil; hot water circulation loop A uses a circulation water pump for forced circulation between the fresh air heating coil and the plate heat exchanger. There are two circulation water pumps, and the two pumps are connected in parallel. The two pumps work simultaneously to avoid the situation where the hot water stops flowing due to pump failure. The pumps use fixed-frequency pumps with a constant water volume to avoid the situation where the water flow decreases due to the decrease of the pump frequency.

[0019] Furthermore, the fresh air heating coil can be set at the inlet of the modular air handling unit or other fresh air intake points, directly contacting the outdoor low-temperature fresh air to heat the fresh air and protect the air handling coils at the back end from the risk of freezing and cracking. The plate heat exchanger is placed inside the building and is used to transfer heat between two hot water circulation loops. The plate heat exchanger does not directly contact the outdoor low-temperature fresh air and is placed in a machine room without the risk of freezing and cracking, avoiding the risk of freezing and cracking from the source.

[0020] By adding the hot water circulation loop A, the system ensures a stable and sufficient hot water flow rate for the fresh air heating coil, preventing it from freezing and cracking due to fluctuations in the hot water flow rate.

[0021] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present utility model. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present utility model. Therefore, the present utility model will not be limited to the embodiments shown herein, but rather will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A fresh air heating system for preventing fresh air coils from freezing and cracking in low temperature areas, characterized in that ； The system includes 1 fresh air heating coil, 1 plate heat exchanger, hot water circulation loop A and hot water circulation loop B; the hot water circulation loop A and the fresh air heating coil form a closed loop, the water outlet end of the fresh air heating coil is connected to one end of the water inlet pipe of the hot water circulation loop A, the other end of the water inlet pipe of the hot water circulation loop A is connected to the water inlet A of the plate heat exchanger through a soft connection and a pipe connection reducer, the water outlet A of the plate heat exchanger is connected to one end of the water outlet pipe of the hot water circulation loop A, a circulating water pump is provided on the water outlet pipe of the hot water circulation loop A, the other end of the water outlet pipe of the hot water circulation loop A is connected to the water inlet of the fresh air heating coil, one end of the water inlet pipe of the hot water circulation loop B is connected to the building hot water supply main, and the other end of the water supply pipe of the hot water circulation loop B is connected to the water inlet B of the plate heat exchanger.

2. According to claim 1, a fresh air heating system for preventing fresh air coils from freezing and cracking in low-temperature areas, characterized in that; The water supply pipe of hot water circulation loop B is connected with a butterfly valve, a pressure gauge, a filter, a pressure gauge, a butterfly valve, a flexible connection, and pipe connection reducers in sequence, wherein the pipe connection reducers are close to the side of the plate heat exchanger.

3. According to claim 1, a fresh air heating system for preventing fresh air coils from freezing and cracking in low-temperature areas, characterized in that: The water outlet of the plate heat exchanger is connected to one end of the return pipe of the hot water circulation loop B, and the other end of the return pipe of the hot water circulation loop B is connected to the building hot water return main. An electric regulating valve is arranged on the return pipe of the hot water circulation loop B. The water flow of the hot water circulation system B is controlled by the opening of the electric regulating valve, and then the water temperature of the hot water circulation system A is controlled, so as to control the temperature of the fresh air after passing through the fresh air heating coil.

4. According to claim 1, a fresh air heating system for preventing fresh air coils from freezing and cracking in low-temperature areas, characterized in that; Hot water circulation loop A uses a circulating water pump to force circulation between the fresh air heating coil and the plate heat exchanger. There are two circulating water pumps, which are set in parallel. The two pumps work at the same time to avoid the situation where the hot water stops flowing due to water pump failure. The water pump uses a fixed frequency pump.

5. According to claim 1, a fresh air heating system for preventing fresh air coils from freezing and cracking in low-temperature areas, characterized in that; The fresh air heating coil is installed at the entrance or fresh air intake of the combined air-conditioning box, and is in direct contact with the low-temperature outdoor fresh air. It is used to heat the fresh air and protect the rear-end air handling coil from the risk of freezing and cracking.

6. According to claim 1, a fresh air heating system for preventing fresh air coils from freezing and cracking in low-temperature areas, characterized in that; The plate heat exchanger is placed inside the building to transfer heat between two hot water circulation loops. The plate heat exchanger does not directly contact the low-temperature outdoor fresh air and is placed in a machine room without the risk of freezing and cracking, thus avoiding the risk of freezing and cracking from the source.

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