Numerical investigation of shunt characteristics and structural design of orifice tube diverter

Multi-channel heat exchanger refrigerant maldistribution constitutes a major constraint on performance enhancement. In recent years, gas-bypass distribution methods have garnered increasing attention. This study proposes an orifice tube diverter, wherein the flow distribution is regulated by controlling the aperture size of each branch. A numerical model coupling pressure and flow within the diverter and manifold was established based on UDF, enabling detailed investigation of the diverter's flow characteristics and performance. The principal findings are summarized as follows: An aperture prediction model was developed based on calculated flow resistance inside the diverter. Utilizing an iterative algorithm, the aperture parameters required to achieve the target flow distribution were efficiently and accurately determined. The manifold regulates the flow distribution by adjusting the back pressure. A uniform variation in back pressure does not affect the flow distribution; however, as the back pressure differential increases, the fluid tends to flow out from the upper branch. Deviation from rated flow conditions degraded diverter performance. Horizontal orientation of the diverter was found to maintain stable performance under varying operational conditions. A novel inclined insert manifold was designed to address bidirectional flow maldistribution in dual-purpose heat pump air conditioning systems. This configuration reduced the non-uniformity coefficients for both forward and reverse flow to 0.017 and 0.018, respectively.