In recent years, water (R718) as a kind of natural refrigerant—which is environmentally-friendly, safe and cheap—has been reconsidered by scholars. The systems of using water as the refrigerant, such as water vapor compression refrigeration and heat pump systems run at sub-atmospheric pressure. So, the research on water boiling heat transfer at sub-atmospheric pressure has been an important iss...

some geothermal reservoirs have temperatures below boiling point and therefore natural steam can not be produced for power generation. refrigerant power cycles may be then employed to recover low temperature heat. in this article study is made of the power cycles of six different relligrants and most suitable refrigerants for this purpose are suggested

Chromatography is an analytical technique employed for purification and separation of organic and inorganic substances including characterisation and quantitative measurement of compounds (table). Basically there are two types: l. Gas chromatography (GC), 2. Liquid chromatography (LC). Although discovered in 1906 by Tshett, developed in the 1950s as the GC technique where the mobile phase are g...

the subjects of heat transfer and cooling system are very important topics in the internal combustion engines (ice). in modern cooling systems, low weight, small size and high compactness are the critical designing criteria that requires heat transfer enhancement. boiling phenomenon which is occurred in the water jacket of the ice is one of the methods to increase heat transfer in the coolant s...

Compression molded composites were made from wood particles and a liquefied wood/phenol/formaldehyde co-condensed resin. Based on our previous research, a phenol to wood (P1W) ratio of 2/1 was chosen for this study. The two experimental variables selected were: 1) liquefaction temperature (1500 and 180°C) and 2) cooking method (atmospheric and sealed). Panels were tested in static bending for m...

We evaluated the effect of dilute sodium hydroxide (NaOH) on wheat straw at boiling temperature for removing lignin and increasing the yield of reducing sugar. Various concentrations of NaOH (0.5% to 2%) were used for pretreating wheat straw at 105 °C for 10 min. Scanning electron microscopy, atomic force microscopy, and Fourier transform infrared spectroscopy studies revealed that the 2% NaOH-...

In this study, one type of nano-engineered heat transfer fluids: Water/AOT/Polyalphaolefin (PAO) nanoemulsion fluids are prepared, and their phase change heat transfer properties have been investigated. The Water/AOT/Polyalphaolefin nanoemulsion heat transfer fluids which are thermodynamically stable are spontaneously generated by a self-assembly of dispersed water nanodroplets The results, exp...

Molecules are bound very closely in ice and much less rigidly in water; hence water acquires fluidity and follows the law that water finds its own level by flowing from higher to lower levels. The rigid binding of molecules in water is loosened by heating. When we raise the temperature to nearly 100°C, the molecules are so energized that they get the freedom to leave the folds of gravitation an...

The effect of surface roughness on nucleate boiling heat transfer is not clearly understood. This study is devised to conduct detailed heat transfer and bubble measurements during boiling on a heater surface with controlled roughness. This first of two companion papers discusses details of the fabrication, construction, and operation of the experimental facility. Test pieces are fabricated from...

The heat transfer model of the RELAP5/MOD3.1 (R5M3) code was extensively reviewed and assessed. The most important deficiency of the current version of the code was attributed to its treatment of the transition boiling heat transfer regime. The current transition boiling model significantly underpredicts the heat transfer rate to the liquid phase. Since at low quality conditions the liquid boil...