Ade Liu QQ584680928

Department: Department of Electronic Information Engineering, Electromechanical 05 1 Instructor: Fan Jianhong.

abstract

This paper introduces the development of foreign cleaning technology and the present situation of domestic cleaning machine industry, and points out the gap between domestic cleaning technology and foreign countries and the problems that should be paid attention to. The intelligent electric water heater is controlled by PIC 16C72 single chip microcomputer. Its main control function is not only the control of heating and protection at ordinary times, but also strong intelligence, including automatically adjusting the mixing ratio of cold and hot water according to the temperature set by users and giving a constant temperature. At the same time, the structure, hardware and software design of the system are introduced. This paper introduces the product appearance and electronic circuit design, including alarm circuit and delay circuit, PTC thermistor and its advantages.

Keywords: status quo of single-chip cleaning machine for intelligent electric water heater; single-chip alarm circuit thermistor for intelligent electric water heater

1 Introduction

1. 1 project background and research significance

The clean industry came into being and developed with the process of industrialization and modernization and the needs of social production. All industrial departments have some form of cleaning, but different departments have different levels of attention, dependence and application development. Industrial cleaning is of great significance: it is a necessary means to restore the production capacity of equipment and ensure the continuous high-load operation of production; Cleaning the equipment can effectively prolong the service life of the equipment; Cleaning the equipment is conducive to energy saving and consumption reduction, reducing the amount of cooling water; Cleaning equipment is an effective way to reduce the occurrence of safety accidents. To sum up, it has the purposes of energy saving, consumption reduction, water saving, safe and stable production, improving product quality, accelerating production speed, prolonging equipment service life, reducing environmental pollution, beautiful appearance and human health. For the development of environmental protection in China, it is absolutely necessary to develop a vacuum ultrasonic cleaning and drying system for hydrocarbons. New factories and production lines are being built all over China, and they are gradually becoming "world processing factories". The huge market demand provides a good opportunity for industrial cleaning equipment manufacturers and professional cleaning agent manufacturers to develop rapidly. In view of the good market prospect of this product and the strong support of the country, I think the investment of this project can bring huge economic and social benefits, and it is very necessary to carry out the research on the separation technology of industrial cleaning liquid. At present, most domestic factories use automatic cleaning machines, especially Hitachi automatic biochemical analysis cleaning machines. Because this instrument has a fast detection speed. Good accuracy. Very popular with the vast number of factories. However, the cleaning machine is expensive and complicated to operate. As for the domestic cleaning machine, the domestic cleaning effect is poor or the machine will corrode in a few days. There is still a certain distance between domestic cleaning machines and foreign cleaning machines, in order to reduce costs. It is of great significance to develop a cleaning solution which can be used for automatic heating separation. References [27] [28]

1.2 the purpose of this subject is to study the separation technology of industrial cleaning solution, and the main work contents are as follows:

(1) Design and manufacture of cleaning agent cooling, heating distillation and automatic cleaning agent recovery system.

(2) The process flow of cleaning agent's filtration, precipitation, slag discharge, distillation, temperature control, fluid replacement and internal circulation. Heat transfer oil heating system, cooling, liquid level/temperature sensor, oil-water separator, PLC automatic control system and liquid level/temperature/pressure automatic control system.

(3) Increase explosion-proof measures. Prevent accidental injury to staff caused by instrument liquid explosion.

(4) Selection of raw materials for cleaning solution. .

(5) Research objective: Research on separation technology of industrial cleaning solution.

1.3 Basic requirements and general process of this project design

(1) has good performance, high efficiency and low cost on the premise of meeting the expected functions. Safe and reliable. Simple operation. Convenient maintenance.

(2) Determine the working principle of the heater and select the appropriate mechanism. Draw up the design scheme; The capacity calculation and overall design of each working mechanism of the heater are carried out.

(3) How to improve system security. The water tank cannot be heated directly. To prevent oil-water explosion caused by direct heating, the material of water tank should also be selected, and the power of electric furnace wire should also be selected appropriately. What kind of furnace wire is selected as the material, etc.

(4) Design the size of the water tank container. And the determination of water content, alcohol content, oil content and kerosene content in the mixed solution, as well as the calculation of how long it takes to heat only to completely volatilize water, alcohol, oil and kerosene, and how much heat the electric furnace wire generates during this time. How much heat is consumed by air. And how much heat the steam takes away.

2 Selection of heater

2. 1 overview

Electric wire heater is the earliest and most common heater in electric heaters, such as electric stoves, electric ovens, constant temperature breeding, electric sleeves and other civil electric heaters, such as bread ovens, hair dryers, electric soldering irons and so on. It has the characteristics of simple structure and convenient temperature control of the heating incubator. PTC thermistor is a typical semiconductor resistor with temperature sensitivity. When it exceeds a certain temperature (Curie temperature), its resistance value increases step by step with the increase of temperature. Its resistance increases gradually with the increase of temperature. Resistors often burn out because of excessive heat generated by resistance heating, so when choosing resistors, we should consider preventing the temperature from being too high. In this paper, PTC thermistor is selected as heating element. Because PTC thermistor not only acts as a heating element, but also has the function of keeping the temperature within a specific range, at the same time, it also plays the role of a switch, and can also play the role of overheating protection for electrical appliances. .

2.2 working principle of PTC thermistor electric heating wire heater

The electric heater is based on the principle that resistance electrifies and heats to generate heat. After the electric heating tube is electrified, according to Joule's law Q=I2Rt, the electric heating tube generates heat, and the heat is transferred to the water in the water tank through the medium, so that the water becomes steam or the temperature in the water reaches the volatilization point of oil, and the oil volatilizes. PTC thermistor is not only a heating element, but also a "switch", which has three functions: sensitive element, heater and switch, and is called "thermistor switch". As shown in figure 1 and figure 2, when the current passes through the thermistor element, the resistance wire generates heat, which increases the temperature, that is, the temperature of the heating element increases. When the Curie point temperature is exceeded, the resistance increases, which limits the increase of current, so the decrease of current leads to the decrease of element temperature. The decrease of resistance makes the circuit current increase, and the temperature of the element rises again and again, so it has the function of keeping the temperature in a specific range and also plays the role of switch. The heat source made of this temperature-resistant property can be used as heat elements for heaters, electric soldering iron, clothes dryers, air conditioners, etc. , and can also play an overheating protection role for electrical appliances.

The heating principle of PTC thermistor heater: The heater is heated according to Joule-Lenz Law Q=I2Rt, and the heating temperature is between several hundred and more than one thousand degrees Celsius. The radiated (radiated) heat Q 1 increases with the increase of temperature, that is:

Q 1 = Q-Q2 = I2Rt-[Cm(T-T0)+Cm(T 1-T0)]

In the formula, Q is the total heat provided by electric energy, Q2 is the heat capacity of heating wire and medium, C is the ratio of heating wire, and C0 is the specific heat capacity of medium. M is the heating wire mass, m0 is the medium mass, T0 is the room temperature, t is the heating temperature of the heating wire, and T 1 is the medium temperature. T increases with time at the first power-on. When the energy provided by electricity and the energy lost reach a dynamic balance, the heating temperature T of the heating wire is stable. When the dissipated energy reaches a dynamic balance, the heating temperature T of the heating wire is stable. References [29]

Figure 1 Schematic diagram of direct protection Figure 2 Schematic diagram of indirect protection

2.3 structure of electric heating wire heater

2.3. 1 resistance wire material selection

Generally, Ni-Cr alloy wire is used as heater, because this material has the characteristics of high resistivity and high melting point temperature. In order to make the heat emitted per unit area larger and the temperature higher, the heating wire is spirally wound on the high-temperature resistant and insulating ceramic or mica medium. The power supply is generally connected with iron screws and nuts as shown in Figure 3 and Figure 4 below, and its contacts have two to ten contacts depending on the heater.

2.3 structure of electric heating wire heater

2.3. 1 resistance wire material selection

Generally, Ni-Cr alloy wire is used as heater, because this material has the characteristics of high resistivity and high melting point temperature. In order to make the heat emitted per unit area larger and the temperature higher, the heating wire is spirally wound on the high-temperature resistant and insulating ceramic or mica medium. The power supply is generally connected with iron screws and nuts as shown in Figure 3 and Figure 4 below, and its contacts have two to ten contacts depending on the heater.

Fig. 3 Spiral heating wire

Fig. 4 Connection diagram of iron screw and nut

2.3.2 heating tube t series

This series * * * has three shapes of heating tubes, which can be easily plugged into the heating tube socket, just like plugging and unplugging a light bulb, as shown in Figure 5 below. T series heating pipes are suitable for different use conditions.

Fig. 5 schematic outline of two kinds of heating pipes.

T 1 is used to heat water in a small cup, which is characterized by low tube power. Its horizontal projection is circular, and its area is about 5 cm small. Therefore, it can be easily inserted into cups with both caliber and height. T2 is used to heat the "fast-heating" heating pipe in the deep water level or kettle. It grows into a strip with only one slot, which is used to fix the heating pipe in the socket, so that it can contact the metal plate in the socket and ensure the smooth circuit.

T3 is used to heat water in containers with large cross-sectional area and large capacity. For example, for a large basin of water, using T 1 will be time-consuming, which can't achieve the purpose of rapid heating, and T2 can't ensure that the heating pipe completely extends into the liquid. Therefore, on the basis of T 1, its diameter is enlarged by five times and its depth is increased to 20 cm.

Therefore, the system adopts T3 series heating pipes.

2.3.3 Heating pipe socket

It is used to connect the heating pipe with the temperature probe, such as the bulb socket. After the heating tube is inserted, it is clamped and contacted with the metal contact in the socket, and the power supply circuit is conducted. When the heating pipe needs to be replaced, it is as convenient as replacing the light bulb. There is also an important component on the heating tube socket-the temperature probe. When the temperature needs to be measured, the probe is unscrewed and the measuring loop is connected, so that the measurement can be carried out; When no measurement is needed, screw the probe into the groove of the plug, disconnect the measuring circuit, stop the heating circuit, and protect the probe from corrosion.

Temperature probe

It is mainly composed of thermistor RT, which is placed in the fuse box to protect the thermistor. The fuse box is used to prevent water from invading the contacts on the thermistor and corroding the probe. When choosing not to use the alarm function, the whole probe should be screwed into the groove in the heating pipe socket.

2 2.4 Characteristics of electric heating tube

(1) has stable and reliable performance. The electric heating tube adopts medium power and high density design, which greatly prolongs the service life of the electric heating tube. Stainless steel material above 3 16, corrosion resistance, washability and long service life.

(2) Maintain the water surface dirt remover (foam) with the least workload to remove mineral impurities floating on the water surface and remove surface dirt to the maximum extent. The water tank is equipped with a special solenoid valve to control the drainage regularly, which can completely remove the precipitated minerals and impurities.

(3) Repeated thermal expansion and cold contraction make the water tank scale fall off continuously.

(4) More optimized structural design, which is convenient for inspection and maintenance with common tools.

(5) Safety circuit design: Three-level circuit protection: short circuit, overcurrent and leakage protection, so as to avoid users' worries.

(6) Anti-dry burning design: When the heating temperature of the electric heating element exceeds the limit that the electric heating element can bear, the power supply of the electric heating element will be automatically cut off to protect the electric heating element from being burnt out.

(7) Special heat insulation design: adapt to various working environments and minimize energy loss.

2.5 Three control modes

(1) Switch control: Turn on (off) when receiving signals, and accurately control the temperature.

(2) Time proportional control (PID): According to the change of actual working conditions, fuzzy logic PID algorithm is adopted to automatically correct parameters and adjust variable power, so as to achieve the best temperature energy-saving state.

(3) Proportional control: The intelligent control module (SCR) is used to cut the phase angle output power, and the controller accurately calculates the output control signal, so that the functional output corresponds to the control signal linearly. The control accuracy can be within RH 65438 0%.

2.6 Design important parameters and performance curves

The following are some performance curves often used in electric heating calculation, which are very helpful for our design.

2.6. 1 Resistance temperature characteristics

Resistance-temperature characteristic is usually called resistance-temperature characteristic, which refers to the dependence between zero power resistance and resistance temperature of PTC thermistor at a specified voltage. Zero power resistance means that the power consumption added to PTC thermistor is very low when measuring the value of PTC thermistor at a certain temperature, which makes the resistance change of PTC thermistor caused by its power consumption negligible. The rated zero-power resistance refers to the zero-power resistance measured when the ambient temperature is 25℃.

lgR(ω)

25 Tmin Tc T(℃)

Fig. 6 Resistance-temperature characteristic curve

Action current of Ik when voltage Vk is applied.

Residual current when Ir applies voltage Vmax.

Vmax maximum working voltage

rated voltage

VD breakdown voltage

2.6.2 Voltammetric characteristics (Voltammetric characteristics)

Voltage-current characteristics, referred to as volt-ampere characteristics, indicate the interdependence of voltage and current when PTC thermistor and electric load reach thermal balance.

I (a)

Inverse dynamics

Vmax VD V

Fig. 7 Voltammetric characteristic curve

Action current of Ik when voltage Vk is applied.

Residual current when Ir applies voltage Vmax.

Vmax maximum working voltage

rated voltage

VD breakdown voltage

The volt-ampere characteristics of PTC thermistor can be roughly divided into three regions: the region between 0 and 0-Vk is called linear region, where the relationship between voltage and current basically conforms to Ohm's law, and there is no obvious nonlinear change, which is also called non-action region. The area between VK and Vk-Vmax is called the jump zone. At this time, due to the self-heating of PTC thermistor, with the increase of voltage, the resistance value jumps and the current decreases, so this area is also called the action area. The region above VD is called the breakdown region, where the current increases with the increase of voltage, and the resistance of PTC thermistor decreases exponentially, so the higher the voltage, the greater the current, the higher the temperature of PTC thermistor and the lower the resistance, which will soon lead to the thermal breakdown of PTC thermistor. Voltammetric characteristic is an important reference characteristic of overload protection PTC thermistor.

2.6.3 Current-time characteristics (I-t characteristics)

The current-time characteristic refers to the characteristic that the current changes with time in the process of applying voltage to PTC thermistor. The current at the moment of electrification is called the initial current, and the current at the time of thermal balance is called the residual current.

Fig. 8 Current-time characteristic curve

At a certain ambient temperature, an initial current (action current is guaranteed) is applied to the PTC thermistor, and the action time is the time when the current passing through the PTC thermistor is reduced to 50% of the initial current. The current-time characteristic is an important reference characteristic for automatic degaussing PTC thermistors, delayed starting PTC thermistors and overload protection PTC thermistors. References [25][26]

Parameters related to thermal effect

(1) dissipation coefficient δ: The ratio of the variation of power consumption in the resistor to the corresponding temperature variation of the element is called dissipation coefficient, and the unit is W/℃. Dissipation coefficient is a parameter to characterize the heat exchange ability between resistor and surrounding medium, and it is also one of the most important parameters in the application of PTC elements. On the premise of certain material formula and process, the Curie temperature and lift-resistance ratio of PTC itself are basically unchanged, while other performance parameters of PTC devices are determined by its structure, shell and heat dissipation conditions. Dissipation coefficient is a comprehensive expression of these conditions. Therefore, the action time and recovery characteristics of PTC elements are related to the dissipation coefficient. For high-power heating components, the heat dissipation coefficient is more important, which directly affects the power output.

When voltage is applied to PTC thermistor, due to power consumption. The temperature of the resistor gradually rises, and at the same time, it dissipates heat to the surrounding medium until the temperature of the resistor reaches stability, at which time all the power consumed is diffused into the medium. The ratio of the power consumption variation △P of the resistor to the temperature variation △T of the resistor is the dissipation coefficient δ.

The heat dissipation coefficient is very important for the structural design of various heating devices. As long as the device structure is slightly modified, the electrical parameters can be greatly improved. However, for a long time, many engineers have been troubled by the research of PTC materials and formulas, which is a great pity.

(2) Thermal time constant ε: This parameter is very important when there is a temperature sensor in the system. Thermal time constant is defined as: under the condition of zero power, when the ambient temperature suddenly changes, the temperature change of the resistance is 63% of its initial temperature difference. 2% of the required time, expressed by ε.

(3) Heat capacity C: The heat required for resistance temperature increase 1℃ is called heat capacity, and the unit is j/℃, and c = ε δ.

(4) Heat transfer conditions: there is a temperature difference. Heat: the heat absorbed or released by an object during heat transfer.

There are three ways of heat transfer: conduction (heat is transferred along an object), convection (heat is realized by the flow of liquid or gas) and radiation (heat is directly emitted from a high-temperature object).

(5) Vaporization: the phenomenon that a substance changes from a liquid state to a gas state. Mode: evaporation boiling, evaporation should absorb heat.

The factors that affect the evaporation rate are: ① liquid temperature, ② liquid surface area and ③ air flow on the liquid surface. Evaporation has a cooling effect.

(6) Specific heat capacity C: material per unit mass, temperature

The heat absorbed when the temperature rises by 65438 0℃ is called the specific heat capacity of the substance. Specific heat capacity is one of the characteristics of matter, and the unit is coke/(kg℃). The specific heat capacity of water in common substances is the largest. C water = 4. 2×103j/(kg℃) Physical meaning: it means that the mass is 1 kg, and the heat absorbed by 1℃ is 4. 2× 103 Joule.

(7) heat calculation: q- discharge = cm ⊿t- drop q- inhalation = cm ⊿t- liter. Q is directly proportional to c, m and ⊿ t, and inversely proportional to c, m and ⊿ t.

(8) Definition formula of electric power: P=W/t Common formula: P=UI W=Uit Q suction = cm δ t. References [2 1]

2.7 Design and calculation of electric heater

2.7. The thermal design steps of1electric heater are generally carried out in the following four steps:

(1) Calculate the power and time required for heating from the initial temperature to the set temperature.

(2) On the premise of maintaining the temperature of the medium unchanged, calculate the actual power required to maintain the temperature.

(3) Heat loss of equipment and its air.

(4) According to the above two calculation results, select the type and quantity of heaters. The total power is the maximum of the above two powers, and 1 is considered. 2 coefficient.

Heat calculation

(1) Power required for initial heating

Kw = (c1m1△ t+c2m2 △ t) ÷ 864/p+p/2, where C 1C2 is the specific heat of the container and the medium (Kcal/Kg℃) respectively.

M 1M2 is the mass of container and medium (Kg) respectively.

△T is the difference between the required temperature and the initial temperature (℃)

H is the time required for the initial temperature to be heated to the set temperature (h)P is the heat dissipation of the container at the final temperature (Kw).

(2) the power required to maintain the constant temperature of the medium

KW=C2M3△T/864+P

Where: M3 kg/hour of culture medium is added every hour.

(3) the power required to maintain the constant temperature of the medium

KW=C2M3△T/864+P

Where: M3 kg/hour of culture medium is added every hour.

(4) The physical characteristics of the thermistor are expressed by the following parameters: resistance value, B value,

① resistance value: RT (kω)

The resistance of thermistor has an exponential relationship with temperature, which can be approximately expressed as:

①

Where: R2: resistance (kω) at an absolute temperature of T2(K)

R 1: resistance (kω) at absolute temperature T 1(K).

B: b value (k) in the temperature range of (t1-t2).

Fig. 9 Power density selection curve of air, gas, water and steam heating (electric heating shell is stainless steel, heat resistant 10000C).

②: b value (k)

The value of b is determined by the conductance activation energy of thermistor, which is a parameter reflecting the change speed of thermistor resistance with temperature, and the expression is:

②

Where: b: (t 1-t2) b value (k) in the temperature range.

R 1: resistance (kω) at absolute temperature T 1(K).

R2: resistance (kω) at an absolute temperature of T2(K)

(5) Theoretical analysis of calculation method of heat loss of heating equipment According to the heat transfer theory, the total heat loss Q on the surface of heating equipment can be calculated by the following formula.

Q=qpj？ S( 1)

Where s is the total heat dissipation surface area of the equipment, m2.

QPj-total average heat flux, W/m2.

Therefore, the fundamental problem here is how to obtain the value of the total average heat flux qpj. Theoretically, there are three methods to calculate the total average heat flux density: heat flux measurement method, heat conduction and heat transfer method and convection heat transfer method.

A heat flow test method: the heat flow test method refers to directly measuring the heat flow values of different parts of the equipment surface or different temperature areas with a heat flow meter, and then taking the average value as the final result. In practical engineering, there are many parts of some devices that cannot be detected by heat flow meter, and the detection results are very one-sided, so this method is not accurate and only suitable for rough estimation on site. Therefore, this system does not use it.

B The calculation method of heat conduction and heat transfer is based on Fourier law of heat conduction, and the heat flow value is calculated when the temperature of inner and outer walls and the thermal resistance of insulation layer are known (the thermal resistance of equipment steel wall can be ignored). Its calculation formula is

③

(3) where qi—— is local heat flux, W/m2.

Δ I —— converted local insulation layer thickness, m

λ-thermal conductivity of thermal insulation material, W/m? ℃

TM-temperature of inner wall of water tank,℃

Tbi—— Temperature of outer wall of water tank,℃.

Here, we think that the uneven distribution of temperature field on the external surface of equipment is due to the damage of thermal insulation layer, which leads to the decrease of thermal resistance (λ/δi). In general, the thermal conductivity of materials is basically unchanged, so theoretically, it can be considered that the reason for the decrease of thermal resistance is the damage and thinning of insulation layer. But in fact, the insulation layer is not uniformly thinned, but is destroyed in various local situations. Here, only the converted thickness of the insulating layer is used to indicate the degree of damage. The value of Δ i passes the local heat flux test, and then is calculated by Formula (2). The total average heat flux is

④

⑤

⑥

I.e. the average value of local heat flow weighted by local area Si.

The accuracy of this method will be greatly affected, because it needs to calculate δi through local heat flow test. And the calculation is complicated, so this scheme is not adopted in this system.

Convective heat transfer method

The convective heat transfer method is based on the natural convective heat transfer between the external surface of the equipment and the surrounding space. When the external surface temperature tbi, ambient temperature t0 and air flow rate V of the equipment are known, the total average heat flow qpj can be calculated by Formula (3) and the following formula.

⑦

Where α is the convective heat transfer coefficient between the external surface of the equipment and the environment, W/m2.

For the secondary system water tank and other equipment, the following formula (4) is adopted.

⑧

Substitute formula ⑧ into formula ⑧, and get ⑨ after completion.

Through the infrared thermal image test, the accurate distribution result of the temperature field on the outer surface of the equipment, that is, the tbi value, can be obtained, so that the value of the total average heat flow qpj can be calculated. Obviously, the core of calculation is to find the average wall temperature weighted by surface temperature. References [22] [24]

2.8 design and calculation example of electric heater

There is a closed container with a width of 500mm, a length of 1200mm, a height of 600mm and a container weight of 150Kg. It contains 500mm high water, and the container is surrounded by 50mm thick insulation layer made of silicate. The water needs to be heated from 15℃ to 70℃ within 3 hours, and then the water temperature in the water tank should be kept constant 15 minutes. How much power is needed to reach the required temperature. Technical data:

1, specific gravity of water: 1000kg/m3.

2. Specific heat of water: 1kcal/kg℃

3. Specific heat of steel: 0. 12 kcal/kg℃.

The surface loss of water at 4.70℃ is 4000W/m2.

5. Insulation loss (at 70℃) is 32W/m2.

6. Container area: 0.6m2.

7. Insulation layer area: 2.52 m2.

Power required for initial heating:

Heating of water in the container: c1m1△ t =/kloc-0 /× (0.5×1.2×1000 )× (70-15) =/kloc.

Heating of the container itself: C2M2△ T = 0.12×150× (70-15) = 990 kcal.

Average water surface heat loss: 0.6m2× 4000w/m2× 3h×1/2× 864/1000 = 3110.4kcal.

Average heat loss of insulation layer: 2.52m2× 32w/m2× 3h×1/2× 864/1000 =104.5kcal.

(Consider 20% abundance)

The energy required for initial heating is (16500+990+3110.4+104.5) ×1.2 = 70258.8 kcal/kg℃.

Power required for operation:

Heat required for heating make-up water: 20kg/h× (70-15 )×1kcal/kg℃ =1100kcal.

Water surface heat loss: 0.6m2× 4000w/m2×1h× 864/1000 = 2073.6kcal.

Heat loss of insulation layer: 2.52m2× 32w/m2×1h× 864/1000 = 69.67 kcal.

(Consider 20% abundance)

The working heat energy is (1100+2073.6+69.6) ×1.2 = 6486.54 kcal/kg℃.

Working heating power: 6486.54 ÷ 864 ÷1= 7.5kw.

The power of initial heating is greater than the power required for operation, and the selected power of the heater should be at least 27. 1kw.

The final heater power is 7kw. Four 7KW electric heating tubes are selected to heat the water tank at the same time.

2.9 composition of electric heater

The composition of the electric heater is as follows: Figure 10.

2. 10 Use conditions and maintenance methods

(1) There are no special requirements for the quality of sewage, kerosene water and gasoline.

(2) ambient temperature >; 4℃, humidity ≤90%RH.

(3) Water and electricity are in place and the shell is grounded.

(4) It is recommended to clean the water tank regularly. (Half a year is a cycle).

(5) If the electric heater is not used for a long time, press the drain button to drain the oil and water in the water tank.