Energy Systems
Mohammed Ridha Jawad Al-Tameemi; Samir Yahya; Saadoon Abdul Hafedh; Itimad D. J. AZZAWI
Abstract
A thermodynamic evaluation is conducted on a combined heat and power system integrating a gas turbine (GT), a heat exchanger (HX1), and an organic Rankine cycle (ORC). Traditionally, ORC bottoming GT cycle is limited to mechanical power production. The novelty of this study is to recover wasted heat ...
Read More
A thermodynamic evaluation is conducted on a combined heat and power system integrating a gas turbine (GT), a heat exchanger (HX1), and an organic Rankine cycle (ORC). Traditionally, ORC bottoming GT cycle is limited to mechanical power production. The novelty of this study is to recover wasted heat from the GT cycle in multistage, which is used for the simultaneous production of mechanical power and hot water supply. In the first stage, the HX1 recovers heat from the GT cycle compressed air to heat the water stream. In the second stage, the ORC cycle recovers thermal energy from the GT turbine exhaust stream to produce extra mechanical power with the remaining latent heat used to heat the water. Two models are proposed for comparison using ASPEN Plus software linked with the RAFPROP database. The modelled GT, in this study, is adopted from an actual machine. The steady-state results show that the combined system achieves 51.55% thermal efficiency compared with a standalone GT efficiency, which is only 21%. The thermal efficiency is divided into 24% mechanical power and 27.55% thermal load. The output hot water temperature is 65 oC. The outcomes of increasing the GT pressure ratio (12-25) are higher combined cycle net power output by up to 16% with a 9.5% reduction in the thermal energy rejected to the environment. Also, the GT efficiency increases from 20% to 22.5%; however, the final water temperature declines from 67 oC to 60 oC, which is still appropriate for various heating applications.
Energy Systems
Armin Emamifar
Abstract
In this research, the thermodynamic analysis of a two-stage absorption compression refrigeration system employing a flash tank with indirect subcooler is presented. The absorption cycle uses LiBr-water solution as the working fluid and prepares the high temperature medium for the bottoming cycle, which ...
Read More
In this research, the thermodynamic analysis of a two-stage absorption compression refrigeration system employing a flash tank with indirect subcooler is presented. The absorption cycle uses LiBr-water solution as the working fluid and prepares the high temperature medium for the bottoming cycle, which is a two-stage compression refrigeration system with R744 refrigerant. The thermodynamic analysis indicates that the proposed system decreases the required electrical work and the total exergy destruction rate results in the improvement of the overall COP and total exergy efficiency. The results are compared with the same system without the subcooler and a simple cascade absorption compression refrigeration system. It was found that the overall COP and the total exergy efficiency of the proposed system are 7.86% and 11.21% higher than the system without the subcooler. These enhancements are 11.42% and 16.48% in comparison with the simple cascade absorption compression refrigeration system. Moreover, the effect of the generator temperature, condenser temperature, cascade condenser temperature, evaporator temperature, and the intermediate pressure of the compression section on the system electrical work, overall COP, total exergy destruction rate, and the total exergy efficiency of the proposed system are discussed.
Energy Systems
Moses EMETERE; Samuel Sanni; O Dauda; A Akinsiku; O Osunlola; A Adejumo
Abstract
The mode of operation of mini parabolic solar panels made of germanium, mild steel and aluminium were investigated experimentally, as means of providing heated water on a farmland; the process was also modelled. Angular adjustments of the solar collectors from 70-90o were adopted in order to determine, ...
Read More
The mode of operation of mini parabolic solar panels made of germanium, mild steel and aluminium were investigated experimentally, as means of providing heated water on a farmland; the process was also modelled. Angular adjustments of the solar collectors from 70-90o were adopted in order to determine, the best material of construction for the parabolic solar collector and the angular orientation with the highest heat collection tendency and absorption rate. The highest quantity of adsorbed heat/best heating effect of the solar collector was obtained at an angular orientation of 80o for mild steel and aluminium. It was also observed that, the parabolic solar collectors have their optimum exposure times, after which, the heating rate drops or there is loss of heat from its surface. The experimental and model estimates, in terms of heat absorption for the mild steel solar collector at 70 and 90o angular tilts, shows that, the optimum heating time was 40 minutes while at 80o, the optimum heating time was found to be 50 minutes.
Energy Systems
Moses EMETERE; Isaac Odun-ayo
Abstract
This research focuses on the need for preserving fruits in rural areas to prevent waste. The solar drier is made of vital chambers i.e. the concentrator chamber (that harvests the solar irradiance), the transport pipe (that transports the heat generated by convection) and hanger chamber (where the fruits ...
Read More
This research focuses on the need for preserving fruits in rural areas to prevent waste. The solar drier is made of vital chambers i.e. the concentrator chamber (that harvests the solar irradiance), the transport pipe (that transports the heat generated by convection) and hanger chamber (where the fruits are placed). The temperature within the concentrator chamber and hanger chamber was monitored. The design allowed heat transfer by convection from the collector to the chamber at an efficiency of 92 %. The design allowed the temperature build up in the solar collector to be transported faster through hanger chamber with the help of incorporated detachable low power dc fan. This arrangement makes the dryer to either operate in the natural convection dryer mode (without the fan) or as a forced convection dryer (with the fan attached). It is observed that the forced convection provided higher air in-flow and hence greater drying capability. However, regions with moderate precipitation may have challenges of delayed fruit drying and growth of microorganism over the surfaces of the dried fruit.
