1.1 Working Principle of Vacuum Boiler Water Heater Unit
The vacuum water heater unit developed by our company is a heat exchange equipment that heats water by boiling and condensing the heat medium, and transferring heat through a heat exchanger. It consists of an evaporation heat exchanger and a condensation heat exchanger. The evaporation heat exchanger is equipped with a boiler combustion chamber and a convection heating surface. The heat released by fuel combustion heats the heat medium water to produce saturated steam under the corresponding pressure. The steam rises into the condensation heat exchanger, condenses and releases latent heat of vaporization, transferring heat to the hot water in the heat exchanger, heating the water to a certain temperature and sending it to the heat user. The condensed water returns to the evaporation heat exchanger for evaporation and vaporization, continuously supplying heat to the outside world. Therefore, the heat medium water continuously circulates in the closed body in a cycle of "boiling = evaporation = condensation = heat medium water". No condensation water needs to be added, and there is no risk of dry burning.
1.2 Performance Characteristics of Vacuum Boiler Water Heater Unit
(1) Safe and Reliable
① The unit always maintains a negative pressure state during operation, and is not a pressure vessel. There is no danger of pipe bursting or explosion, and no accidents caused by lack of water in the unit. Safety protection interlocks such as vacuum pressure control switch, unit overheating protection device, heat medium resistance, and fusible safety valve are set to fundamentally ensure the safe operation of the unit.
② Without water treatment equipment, the boiler heating surface can operate for a long time without scaling, fundamentally solving the accidents caused by scaling, such as boiler pipe bursting, drum bulging, and overheating of heating surface steel.
③ Since the boiler water is in a saturated state during operation, the oxygen content in the boiler water is extremely low, and oxygen corrosion of the boiler no longer exists, greatly extending the service life of the boiler.
(2) No License Required
According to document No. [2002] 288 issued by the State Administration of Quality Supervision, Inspection and Quarantine, users do not need to go through installation and use registration procedures with the quality and technical supervision department when installing and using vacuum water heater units.
(3) Long Service Life
The heat medium added to the unit is softened water after softening treatment. It does not increase or decrease during the operation of the unit, and is sealed in the water wall of the unit. It transfers heat between the heating surface and the exchanger of the unit without direct contact with the flame or flue gas. Moreover, the heat load is uniform and stable, reducing thermal stress. There is no condensation corrosion outside the unit, and there is no danger of pipe bursting or explosion. Therefore, the service life is long, up to more than 30 years.
(4) Safe, Environmentally Friendly, and High Efficiency
① Because the medium water temperature is relatively low, the boiler flue gas temperature can be reduced to a very low level without setting a tail heating surface, and the flue gas heat loss is small.
② The overall temperature level of the boiler body is low, and the heat dissipation loss is small, so the boiler thermal efficiency is high.
③ After a period of operation, the heating surface of ordinary boilers will be affected by scaling, which will affect heat transfer and reduce the boiler thermal efficiency (according to authoritative institution tests, the thermal efficiency of ordinary boilers will decrease by 2-3% after one heating season, and will decrease more after 2-3 years of operation. After 5-6 years of operation, its thermal efficiency is only 50-60%, resulting in huge energy waste). Vacuum boilers do not scale during operation, the heat transfer resistance is small, the heat transfer effect is good, and the energy saving effect is obvious.
(5) Small Size and Space Saving
The vacuum water heater unit has a compact structure design, small footprint, small volume, and small amount of heat medium water and small heat capacity. Therefore, the thermal inertia is small, and it responds sensitively to load changes. The hot water preheating time is short after the boiler is started, reducing fuel waste.
(6) Automatic Operation
The unit adopts PLC programmable control, and all electrical components are well-known brands. It has automatic water temperature control, automatic fault diagnosis and safety protection, and can be operated without personnel.
(7) Low Maintenance Cost
The unit control system adopts advanced microcomputer program control and fully automatic operation. It does not require professional operators and can be operated without personnel.
(8) Easy to Clean Heat Exchanger  
The unit has a built-in straight tube heat exchanger, which is easy to disassemble and clean, and easy to clean and maintain.
The boiler does not require water treatment equipment, saving water quality testing and water treatment equipment operating costs. No annual inspection is required, and maintenance management costs are low.
(9) Easy Installation
The unit adopts a built-in straight tube heat exchanger and does not need to be equipped with external equipment such as water treatment instruments, heat exchangers, and circulation pumps. It only needs to be connected to external pipelines to be used, greatly reducing installation requirements and costs.