Brief introduction to the principle of air conditioning billing system

The traditional heat metering technology can theoretically calculate the energy of a single household. As long as the temperature difference is obtained, the flow rate of heat carrier can be changed to calculate the energy consumption of users. However, because the accuracy requirements of flowmeter and thermometer are very strict, and temperature and flow are the key parameters in the integral equation, there is a dilemma in statistics: one is the equipment with great difficulty and poor accuracy, the measurement is inaccurate and the data basis is unscientific; Second, high-precision metering equipment is expensive and difficult to popularize in a large scale.

1997 puts forward the central air-conditioning billing system, which measures the usage of central air-conditioning from the perspective of the system. Based on the traditional heat metering theory, the equivalent energy theory is put forward, that is, the time equivalent is used to convert the usage of central air conditioning to simplify the complicated problems. 1, Introduction of charging principle

The time sampler is connected with the fan coil and the temperature controller. The sampler detects the state of the electric valve in real time, detects the working state of the fan coil in high, medium and low gear while obtaining the opening signal of the electric two-way valve, and automatically accumulates the effective running time of each gear. The signal is transmitted to the air-conditioning billing instrument through the communication manager, and the air-conditioning billing instrument communicates with the central workstation, manages the database, and realizes the functions of meter reading, charging, control and management. The system takes the effective equivalent time of users using air conditioners as the charging basis to realize the charging purpose of "using more and using less". The above measurement was carried out under the condition that the central air conditioning system was running effectively. If the air conditioning system is not running, there is no charge.

The following system flow chart:

When the system provides cooling (or heating), the user's electric valve is opened, the user's fan coil unit operates effectively, and the charging will begin. The user's effective equivalent time is:

T total =K period ×K coil ×(K height× t height +K middle× t middle +K low× t low)

These include:

T total: the total equivalent time of the fan-coil unit, in h.

K-coil: cooling and heating plate for each coil.

K height: gear coefficient of high-grade fan coil unit.

K: Gear coefficient in the middle range of fan-coil unit.

K low: the gear coefficient of fan-coil unit is low.

T height: the effective service time of high-grade fan coil units.

T: Effective service time of fan coil.

T low: Effective service time of low-grade fan coil units.

K period: time period coefficient 1, system introduction.

According to the principle of heat exchange in thermodynamics, the "energy-based" billing system accumulates the "heat" exchanged by users in the process of using central air conditioning, realizes the household metering of central air conditioning, and then scientifically and reasonably allocates the total cost according to the proportion of "heat" used. The system can effectively reduce the energy consumption of air conditioning and make the operation and management of central air conditioning more scientific, reasonable and standardized.

The "energy-based" charging method is mainly used in shopping malls, clubs, factories and other large-area metering occasions that need to be divided into areas (the diameter of the metering area is above DN50) and metered by layers.

2. System characteristics

Based on the heat exchange principle in thermodynamics, it is scientific and reasonable.

Electronic system, small external interference and long service life.

L Using a flowmeter without moving parts, the measurement is more accurate.

L Four-wire high-precision paired temperature sensor is adopted.

The software system is powerful, and it is easy to realize the functions of charging by time and copying data sets.

3. System principle

According to the principle of heat exchange, the "energy-type" charging system measures the outlet temperature T 1, the inlet temperature T2 and the instantaneous flow rate Q of the energy-carrying medium (liquid water) in the heat exchange system in real time, and calculates the cold or heat value consumed by the system according to the thermodynamic energy calculation formula. When T 1 is greater than T2, the cooling capacity is integrated, and when T 1 is less than T2, the heat capacity is integrated, and the cooling capacity and heat capacity are saved.

The calculation formula is as follows:

Among them:

L q- heat released or absorbed (j or wh);

LQM-mass flow of water flowing through the electric energy meter (kg/h);

Lqv-volume flow of water flowing through the electric energy meter (m3/h);

Lρ—— rho-density of water flowing through the electric energy meter (kg/m);

L δ h-enthalpy difference of water at inlet and outlet temperature of heat exchange system (J/kg);

L t-heat exchange time (h).

Provided by Konglv.com HVAC experts.