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A stepped short tube orifice (SSTO) consisting of two serial-connected short tube orifices with different diameters was recently proposed as an inexpensive expansion device in air conditioning/heat pump system. In this study, a split air conditioner/heat pump employing stepped short tube orifices was investigated experimentally to further evaluate the performance of the SSTO air conditioner/heat pump system. At first, the mass flow rate of refrigerant (R-22) through stepped short tube orifices and an original expansion device were studied in both cooling and heating flow directions to verify the throttling capacity difference of these two type of expansion devices. Then, the influence of geometric sizes of SSTOs, refrigerant charge amount and environment temperature on the performance of the SSTO air conditioner/heat pump were examined. Besides, the performance of the SSTO systems also compared with that of the original system with capillary tube under nominal and varying conditions. The results show that 18# SSTO system performed the best COP among all the five SSTO systems and one original system in nominal cooling and heating conditions, though the heating capacity of the 18# SSTO system was slightly inferior to that of the original system due to the insufficient throttling capacity of 18# SSTO in heating mode.

An expansion device of two capillary tubes with a by-pass check valve is popularly used in domestic heat pump systems. In order to reduce the manufacturing cost and improve reliability of the heat pump systems, a stepped short tube orifice consisting of two serial-connected short tube orifices with different diameters is employed as an alternative. The effects of upstream pressure, downstream pressure, upstream degree of sub-cooling and the geometric sizes of stepped short tube orifices on mass flow rate difference between forward flow and reverse flow of R-22 through stepped short tube orifices were investigated in this study. The results showed that there was a distinguishing mass flow rate difference between forward flow and reverse flow of R-22 through stepped short tube orifices under upstream pressure ranged from 1460 kPa to 1940 kPa, downstream pressure ranged from 420 kPa to 680 kPa and degree of sub-cooling ranged from 2 to 12 °C. The mass flow rate difference is about 10 kg/h between forward flow and reverse flow of R-22 through the stepped short tube orifice with sizes of D1 = 0.8 mm, D2 = 1.0 mm, L1 = 3 mm, L2 = 6.5 mm at the upstream pressure of 1940 kPa, downstream pressure of 500 kPa and the degree of sub-cooling ranging between 2 °C and 12 °C.

A needle-type coaxial probe for the measurement of radio frequency and microwave permittivity of biological samples is studied both theoretically and experimentally. The probe is obtained by a slanted cut, and therefore the radiation aperture is elliptical. Both theoretical analysis and experiments show that the measurement sensitivity is improved with the increased bevel angle of the probe. Calibration results using water and air at low frequencies are in agreement with theoretical calculations. Measurements on three biological samples (sonicated DNA macromolecules, water solutions of protein (the protamine), and in -aminocaproic acid) were made from 1 MHz to 1 GHz. All the measured results are in very good agreement with similar tests obtained from the same materials using a standard probe. The theoretical and experimental results show that the probe improves measurement sensitivity and it facilitates insertion into some test samples. >

In this paper some simple and effective methods are presented for solving electromagnetic problems of dielectric-loaded rectangular waveguides. The procedures are demonstrated and the accuracy is shown for waveguides with three different types of dielectric filling.

In this paper two simple and effective methods are presented for solving electromagnetic problems of rectangular waveguides, loaded with lossy dielectrics. The procedures are demonstrated and the accuracy is shown for waveguides with three different types of dielectric filling.

In this paper an improved method is presented for waveguides loaded with lossy dielectric or magnetic materials. The accuracy of this method is shown for waveguides with three different types of filling.