No abstract

In this study the thermal characteristics of horizontal mantle heat exchangers are investigated for application in active solar water heaters. Some important parameters such as flow rate, thermal short circuit, average temperature, and convection heat transfer coefficient and inlet velocity have been investigated too. The results show that the thermal efficiency of the storage tank is critically impaired by the effect of short circuit phenomenon and mixing caused by turbulence. List of symbols AThe area between tank and mantle (m 2 ) C p Specific heat at constant pressure (J/kg K) h o Mean convective heat transfer coefficient of mantle wall (W/m 2 K) _ m m Inlet mass flow rate into mantle (L/min) t Time (s) T in Average temperature of inlet to mantle (°C) T out Average temperature of outlet from mantle (°C) T m Average water temperature in mantle (°C) T s Average temperature of inner surface of the tank (°C) T ci Temperature of inlet water into tank (°C) V Volume of hot water drawn off (L) v j Volume of j th layer (m 3 ) E out Storage energy into the tank before draw offs E st Used energy of tank during draw offsGreek letters q Density (kg/m 3 ) g Efficiency

No abstract

No abstract

In many industrial plants including petrochemicals and refineries, raw hydrocarbons (mostly flammable gas) are released during unplanned operations. These flammable gases (usually called flare gases) are sent to a combustor and the process is called flaring. Flaring wastes energy and produces environmental pollution. Consequently, recovering the flare gases is an important subject in these industries. In this work, an economical and technical analysis is presented for the production of valuable products, namely, liquefied natural gas and natural gas liquids from flare gas. The flare gas of Fajr Jam refinery, a refinery located in the south part of Iran, is selected as a case study. One of the issues in recovering flare gases is the nonconstant flow rate of these gases. For this reason, an auxiliary natural gas flow rate is employed to have a constant feed for the flare recovery process. The Poly Refrigerant Integrated Cycle Operations (PRICO) refrigeration cycle is employed for producing liquefied natural gas and natural gas liquids. In the PRICO cycle, the mixed refrigerant is used as the working fluid. The other issue is the existence of H 2 S in the flare gases. The main idea is that the flare gas components, including H 2 S, have different boiling points and it is possible to separate them. Consequently, flare gases are separated into several parts during a number of successive cooling and heating stages and passing through phase separators. It is shown that the proposed flare gas recovery process prevents burning of 12 million cubic meters of the gases with valuable hydrocarbons, which is almost 70% of the current flare gases. Furthermore, about 11,000 tons of liquefied natural gas and 1230 tons of natural gas liquids are produced in a year. Finally, the economic evaluation shows a payback period of about 1.6 years.