Abdulghani A. Al-Farayedhi

Simulation of a hybrid liquid desiccant based air-conditioning system

A hybrid open-cycle vapor absorption and liquid desiccant system using LiBr for the process of absorption and dehumidification has been simulated. The simulation model of the hybrid cycle is formulated with a partly closed-open solar regenerator for regenerating the weak desiccant and a packed tower dehumidifier for the dehumidification of ambient air. The air is first dehumidified in the dehumidifier and then sensibly cooled in the evaporator. Subroutines for each component of the cycle have been used in order to calculate the varying parameters at all points in the cycle. The hybrid model presented is found to be an excellent alternative to conventional vapor absorption machines, particularly in hot and humid climates. The COP so obtained is about 50% higher than that of a conventional vapor absorption machine and is likely to increase further for the conditions which have been discussed.

Thermodynamic analysis of liquid desiccants

Liquid desiccants are widely used in many solar applications. In order to analyze the performance of the system using desiccant technology, the thermophysical properties of desiccants are essential. In particular, the vapor pressure of the liquid desiccant is one of the important properties in air dehumidification. In this paper, an attempt is made to predict this property based on a classical thermodynamics approach and it is found that the predicted values for lithium chloride agree very well with the experimental results. The desired sorption properties can also be obtained by mixing the desiccants, which is another method of developing a new cost-effective liquid desiccant. In this paper, simple mixing rules are used to predict the vapor pressure, density, and viscosity of the desiccant mixture, namely calcium chloride and lithium chloride. It is found that the interaction parameter need not be included in calculating the density and vapor pressure of the above mixture but must be included in predicting the viscosity.

Experimental investigation of SI engine performance using oxygenated fuel

The current experimental study aims to examine the effects of using oxygenates as a replacement of lead additives in gasoline on performance of a typical SI engine. The tested oxygenates are MTBE, methanol, and ethanol. These oxygenates were blended with a base unleaded fuel in three ratios (10, 15, and 20 vol.%). The engine maximum output and thermal efficiency were evaluated at a variety of engine operating conditions using an engine dynamometer setup. The results of the oxygenated blends were compared to those of the base fuel and of a leaded fuel prepared by adding TEL to the base. When compared to the base and leaded fuels, the oxygenated blends improved the engine brake thermal efficiency. The leaded fuel performed better than the oxygenated blends in terms of the maximum output of the engine except in the case of 20 vol.% methanol and 15 vol.% ethanol blends. Overall, the methanol blends performed better than the other oxygenated blends in terms of engine output and thermal efficiency.

Regeneration of liquid desiccants using membrane technology

Liquid desiccants used for many industrial and domestic applications have to be reconcentrated for reuse. Instead of using thermal energy, a method is proposed in this paper to use mechanical energy for regeneration of weak desiccants. The osmotic pressure required to regenerate two such desiccants, namely calcium chloride and lithium chloride, for given operating conditions is predicted, and correlations are developed. It is found that the pressure required for calcium chloride is much less than that of lithium chloride for the same operating conditions.

Second-law-based thermoeconomic optimization of a sensible heat thermal energy storage system

An analytical method for the second-law-based thermoeconomic optimization of a sensible heat-storage system, in which the energy is stored in a large liquid bath from a hot-gas source, is presented. In this approach, monetary values are attached to the irreversible losses caused by the finite-temperature difference heat transfer and pressure drop in the storage system. Results are presented in terms of the optimum number of transfer units as a function of a dimensionless unit-cost ratio, charging time, and reduced temperature difference of the storage system.

Exergy analysis of a liquid-desiccant-based, hybrid air-conditioning system

We present the applicable exergy analysis and estimate irreversible losses that are generated during operation of a hybrid air-conditioning cycle with emphasis on a partly closed solar regenerator that is used to regenerate weak desiccant. The desiccant mass-flow rate has been chosen as the fundamental parameter for analysing the system. We find an optimum mass-flow rate for minimum irreversibility, i.e. maximum exergy. Large irreversibilities occur for high ambient vapor pressures, which tend to decrease the system exergy and overall performance of the regenerator.

Effects of Blending MTBE With Unleaded Gasoline on Exhaust Emissions of SI Engine

The current paper examines the effects of using MTBE as a replacement of lead additives in gasoline on exhaust emissions of a typical SI engine. The MTBE was blended with a base unleaded fuel in three ratios (10, 15, and 20 vol. percent). The emissions of CO, HC, and NOx were measured at a variety of engine operating conditions using an engine dynamometer setup. The results of the MTBE blends were compared to those of the base fuel and of a leaded fuel prepared by adding TEL to the base. With respect to the base fuel, the addition of MTBE decreased the CO emissions, decreased the HC emissions at most operating conditions, but generally increased the NOx emissions. The emissions results for the leaded fuel were comparable to those of the base fuel.

Solar regeneration of liquid desiccants suitable for humid climates

A modified open regeneration system suitable for humid climates is proposed. The upper part of the open solar regenerator is covered with a single glazing where the desiccant can be heated without water evaporation. Evaporation starts at the beginning of the open surface. For this type of regenerator, the regeneration efficiency is defined as the ratio of energy used to evaporate water from the open surface to the total radiation falling on the glaze and open surfaces. The effect of flow length of the regenerator (for the glaze and open surfaces) has been taken into consideration in evaluating regeneration efficiency. Effects of some of the operating parameters are briefly discussed in this paper.

Thermal performance analysis of a partly closed-open solar regenerator

This paper presents a modified open regeneration system suitable for humid climates. The upper part of the open regenerator is covered with a single glazing where the desiccant can be heated up without evaporation of water and the evaporation starts at the beginning of the open surface. For this type of regenerator, performance analysis has been made to predict the mass of water evaporated from the weak liquid desiccant to the atmosphere. The regeneration efficiency is obtained for various ratios of glaze surface area to the open surface area for different operating parameters.

Prediction of reformate research octane number by FT-i.r. spectroscopy

Abstract Fourier transform infrared (FT-i.r.) spectroscopy was used to calculate the research octane number (RON) of naphtha feed and reformate during the course of performance evaluation of reforming catalysts. Five absorption regions that correspond to aliphatic and aromatic bands within the mid-infrared region were utilized for developing the correlation for RON estimation. Statistical methods were used to derive third degree polynomial equations which could give a better estimate of engine RON. The technique was found to give excellent correlation (R2 = 0.95) with the engine RON data.