Research On The Performance Of Low-cost Inverter Air Conditioners With Short Tube Orifice

With the gradual saturation of the air-conditioning market and the rise in prices of raw materials such as copper,the production pressure of the air-conditioning manufacturing industry is also increasing.Copper is used as an evaporator,condenser,throttling mechanism and connecting pipes in the air-conditioning system.The cost of copper materials accounts for about 15% of the cost of raw materials for the entire air conditioner..Therefore,reducing the use of copper in the air conditioning system is of great significance for reducing the cost of air conditioner production and improving the competitiveness of the enterprise.As a new type of throttling mechanism,compared with commonly used traditional capillary throttling components,the throttling short tube has a simple structure,consumes less copper,has great advantages in price,and has the high process consistency which makes it easy to install and replace.In addition,since the pressure is distributed along the short tube orifice during the shutdown of the air-conditioning system,the compressor’s starting torque is lower when the system is restarted,and the system performance is more stable.This paper considers the metastable flow of the refrigerant in the throttling short tube,and divides it into subcooled,metastable,and gas-liquid two-phase sections according to the different flow states of the refrigerant.And energy conservation equations,the governing equations of the three regions are listed and solved numerically.Among them,the mathematical model of the gas-liquid two-phase section uses a homogeneous flow model,ignoring the velocity slip between the gas and liquid phases,and the finite difference method is used to solve the governing equation of the gas-liquid two-phase region.The mathematical model can predict the mass flow rate of the refrigerant flowing through the choke tube under the given working conditions and cooling conditions.The mathematical model was programmed by EES,and the flow characteristics of the throttling short tube were theoretically analyzed.Using R410 A as a refrigerant,the effects of upstream pressure,downstream pressure,subcooling,short tube diameter and length on mass flow were explored.And got the following conclusions: under the same conditions,the mass flow of the throttle short tube increases linearly with the increase of upstream pressure,increases with the increase of subcooling and pore size,and decreases with the increase of length,and Under the calculation conditions,the mass flow is hardly affected by the downstream pressure.The reason is that the refrigerant velocity in the short tube reaches the speed of sound at this time,and choking flow occurs.The throttling short tube is used as a throttling mechanism in the air conditioner and R410 A is used as the refrigerant.By changing the throttling short tube type,adjusting the refrigerant charge,changing the compressor frequency and fan speed for the performance of the 12 T and 18 T single-cooled inverter room air conditioners,so that their cooling capacity,power consumption and ISEER energy efficiency value reached the platform standard,which indicates that the throttle tube can replace the capillary tube in small and medium-sized air conditioners.