Alternative refrigerant R-134a is considered to be ozone-friendly and apotential candidate for replacing the refrigerant R-12 in refrigeration and air-conditioningapplications. This paper presents an experimental inve...Alternative refrigerant R-134a is considered to be ozone-friendly and apotential candidate for replacing the refrigerant R-12 in refrigeration and air-conditioningapplications. This paper presents an experimental investigation on condensation heat transfer of thealternative refrigerant R-134a flowing inside a helicoidal pipe with the cooling water flowingthrough the annular helicoidal passage in a counter-flow direction. The heat transfer experimentswere performed for R-134a mass flow flux ranging from 100 to 420 kg/m^2 s with the superheat of theinlet vapor of 2. 8℃ and 8.3℃, respectively. The average Nusselt numbers were experimentallydetermined for a helicoidal pipe with the helix axis of vertical direction. In addition, theobtained experimental results were compared with the results for R-134a condensation in straight andhelicoidal pipes available in the open literature.展开更多
A new instrument was developed for measuring the local moisture content in moist porous media based on the needle-type capacitance sensor and single-chip microprocessor technique. The working principle, the structure ...A new instrument was developed for measuring the local moisture content in moist porous media based on the needle-type capacitance sensor and single-chip microprocessor technique. The working principle, the structure and characteristics of the hardware and software of the instrument were presented. The dynamic response characteristics and reliability of the instrument were experimentally determined. As an example, the instrument was employed to measure the heat and mass transport properties of a moist porous material. The experimental results show that the instrument can be used for measuring the local moisture content in moist porous media and would be an effective tool for determining the heat and mass transport properties in moist porous media.展开更多
文摘Alternative refrigerant R-134a is considered to be ozone-friendly and apotential candidate for replacing the refrigerant R-12 in refrigeration and air-conditioningapplications. This paper presents an experimental investigation on condensation heat transfer of thealternative refrigerant R-134a flowing inside a helicoidal pipe with the cooling water flowingthrough the annular helicoidal passage in a counter-flow direction. The heat transfer experimentswere performed for R-134a mass flow flux ranging from 100 to 420 kg/m^2 s with the superheat of theinlet vapor of 2. 8℃ and 8.3℃, respectively. The average Nusselt numbers were experimentallydetermined for a helicoidal pipe with the helix axis of vertical direction. In addition, theobtained experimental results were compared with the results for R-134a condensation in straight andhelicoidal pipes available in the open literature.
文摘A new instrument was developed for measuring the local moisture content in moist porous media based on the needle-type capacitance sensor and single-chip microprocessor technique. The working principle, the structure and characteristics of the hardware and software of the instrument were presented. The dynamic response characteristics and reliability of the instrument were experimentally determined. As an example, the instrument was employed to measure the heat and mass transport properties of a moist porous material. The experimental results show that the instrument can be used for measuring the local moisture content in moist porous media and would be an effective tool for determining the heat and mass transport properties in moist porous media.
