Sharif Digital Repository

Water and energy supply are two of the key issues human beings must address to attain sustainable development. Humidification-dehumidification technology has been proven to be a cost-effective approach to fulfill the freshwater demand. Particular attention has been given to coupling the humidification-dehumidification cycles with refrigeration, power and other desalination technologies with the aim of enhancing the performance of the combined cycle as well as increasing the amount of produced freshwater, cooling effect, power, etc. This paper provides a comprehensive review of the state-of-the-art investigations in terms of humidification-dehumidification technologies and their integration... 

Control of the air-handling units (AHU) is required to maintain satisfactory comfort conditions with low energy consumption. In the case of failure in sensor fusion systems of AHUs, full-order observers can be used as the supportive tool to provide an acceptable estimation of state variables. In this paper, a multivariable nonlinear model of the AHU is considered in the presence of uncertainties. The indoor temperature and relative humidity are controlled via manipulation of valve positions of air and cold water flow rates. In proposed hybrid control system, full and minimum-order observers are designed for the estimation of indoor temperature and relative humidity. Also, a regulator for... 

Air-handling unit (AHU) is one of the most complex installations that its control is necessary for maintaining satisfactory comfort conditions in buildings with low energy utilization. In this paper, a multivariable nonlinear and minimum phase model of the AHU is considered in the presence of uncertainties. The controller design is divided into two types. The first controller type is for the linearized plant based on decoupled PID-Fuzzy and PD-type Fuzzy controllers. The second type is based on full matrix PID-Fuzzy and pole-placement controllers in which interaction effects are considered. The indoor temperature and relative humidity are controlled via manipulation of valve positions of air... 

In this paper, the performance of a novel HDH solar desalination system equipped with a combination of heat pipe (HP), evacuated tube collector (ETC) and air bubble column humidifier is experimentally investigated. This novel HDH system uses advantages of ETC-HP as a highly efficient thermal absorption and conductor device, and at the same time employs the advantages of an air bubble column humidifier, i.e. high interface area and effective mixing in order to heat the water and humidify the air, respectively. The effects of various parameters including incoming air flow rate into the humidifier, initial depth of water in the humidifier, and adding fluids such as oil and water in the space... 

This paper presents an experimental study on prediction of the early-age creep and shrinkage of concrete with and without silica fumes, trass, ground-granulated blast-furnace slag, combinations thereof, and influences of the proposed Iranian pozzolans. Experiments were carried out under a controlled ambient condition at a temperature of 40° C and a relative humidity (RH) of 50%, and a laboratory ambient condition at a temperature of 20° C and a relative humidity (RH) of 30% in order to collect the required data. Comparisons are made between ACI209-92, BS8110-1986 and CEB1970 prediction models, and an estimation model, based on 28-day results (short-term test method), using the same... 

This study presents a novel set-up for desiccant-based cooling and dehumidification systems. In this cycle, a solid desiccant and conventional combined cooling and power (CCP) systems, based on the ejector refrigeration cycle (ERC) and the organic Rankine cycle (ORC), are integrated to provide dehumidification and cooling, simultaneously. The ERC is integrated with the ORC for devising a self-powered design which has not been done until now. The proposed integrated system is useful for replacing the peak electricity demand with the heat demand, decreasing the pressure on the power grid in humid areas. Dynamic hourly simulation of the proposed system as well as a conventional system were... 

In this study, the theoretical investigation of a novel heat pump assisted humidification-dehumidification desalination system has been carried out. The conventional dehumidifier of the humidification-dehumidification system was removed and the evaporator of the heat pump was utilized for direct dehumidification of air. Besides, the heat pump condenser was used as the saline water heater of the humidification-dehumidification cycle. First, the sizes of the components were calculated at design conditions for fixed input operational conditions namely the ambient air temperature, relative humidity, and inlet saline water temperature. However, the input operating conditions vary at off-design... 

Supersonic separators are used in gas separation processes such as dehumidification of humid air due to high performance and its good pressure recovery. In the present study, a comprehensive numerical and experimental investigation on the hydrodynamic behavior of air as working fluid and dehumidification performance of supersonic separator have been accomplished. The effect of the operational parameters on shockwave's position are examined. The outcomes show that by increasing the pressure level of supersonic separator, relative error between numerical and experimental results decreases from 20% to less than 10%. The effect of the operational parameters and humidity of inlet air on the... 

Discharging unconventional water sources having a high content of inorganic compounds is extremely destructive to the environment. In this research, four novel semi-open-air and closed-air configurations of brine-recycle humidification-dehumidification (BRHDH) systems with zero liquid discharge (ZLD) approach are presented to treat unconventional waters cost-effectively. Bubble-column humidifiers and dehumidifiers are used to have a low initial expenditure, and system multi-staging is implemented to reduce the operating expense of the configurations. The configurations are evaluated for high saline brine treatment using comprehensive energy, exergy, exergoeconomic, and exergoenvironmental... 

In this study, four new indirect heat pump assisted mechanical vapor compression humidification-dehumidification (HDH) systems are proposed and their superiorities over the reference system are demonstrated from thermodynamics and thermoeconomics viewpoints. The proposed models are configured based on an HDH unit and a simple cascade heat pump, an HDH unit and a heat pump with an ejector, an HDH unit and a cascade heat pump with an ejector, and an HDH unit and a vapor injection heat pump. Although employing a heat pump with cascade and ejector configurations improved gain-output-ratio (GOR) and specific power consumption (SPC) values in comparison with the base system, the performance... 

In the recent researches HVAC with a based desiccant dehumidifier with a low ambient impact is more efficient in comparison to the traditional systems. Hybrid desiccant cooling systems can be used to control indoor air quality in buildings. This paper presents an integrated energy, entropy and exergy analysis of a hybrid desiccant cooling system compare to a compression system based on first and second laws of thermodynamic. The main objective is the use of a method called exergy costing applied to a conventional compression system that has been chosen to provide the proper conditioned air for a building in hot and humid condition. By applying the same method for the equivalent hybrid... 

The efficiency of proton exchange membrane (PEM) fuel cell is straightly correlated to the bipolar plate design and fluid channel arrangements. Higher produced energy can be attained by optimal design of type, size, or patterns of the channels. Previous researches showed that the bipolar plate channel design has a considerable effect on reactant distribution uniformity as well as humidity control in PEM fuel cells. This paper concentrates on enhancements in the fuel cell performance by optimization of bipolar plate design and channels configurations. A numerical model of flow distribution based on Navier-Stokes equations using individual computer code is presented. The results gained from... 

In this study, effect of desiccant wheel, heat exchanger and cooling coil will be evaluated on decreasing the wet bulb temperature of entering air to cooling tower and decreasing the outlet cold water temperature. For this purpose, change effect of desiccant wheel parameters will be investigated on wet bulb temperature of outlet air from heat exchanger. After that, optimum parameters and minimum wet bulb temperature will be selected. Then, outlet cold water temperature will be achieved for various cooling coil surface temperature with definition of by pass factor and also by using optimum desiccant wheel parameters and entrance air wet bulb temperature to tower related to cooling coil... 

A hybrid HDH desalination system integrated with a heat pump was experimentally studied. In this system, heat pump's heating was used to raise the temperature of the air entering the humidifier and its cooling effect was used for dehumidification of humid air and freshwater production. In other words, heat pump's condenser works as the heater of the HDH cycle and its evaporator works as the coolant for the dehumidifier of HDH cycle. The effects of different parameters such as mass flow rate of inlet saline water (relative humidity of the air passing the dehumidification section), volume flow rate of the air passing the dehumidification section and ambient air temperature on freshwater... 

The quality of perovskite films plays a crucial role in improving the optoelectronic properties and performance of perovskite solar cells (PSCs). Herein, high-quality CsxFA1−xPbI3 perovskite films with different compositions (x = 0, 5, 10, and 15) are achieved by controlling the amount of cesium chloride (CsCl) in the respective FAPbI3 precursor solution. The effects of CsCl addition on the morphological and optoelectronic properties of the resulting perovskite films and on the performance of the corresponding devices are systematically studied. Introduction of CsCl into FAPbI3 shows a great potential to stabilize the α-FAPbI3 perovskite phase by forming CsxFA1−xPbI3 films with improved... 

Air-handling units (AHUs) are the installations responsible for the control of temperature and humidity inside a space using the heating, cooling, humidifier and drying air components. In this research, a multivariable nonlinear dynamic model of the AHU with one zone in the VAV (variable air volume) system for working in the summer is considered. The indoor temperature, relative humidity and carbon dioxide concentration are controlled via manipulation of the valve positions of the air flow rate, cold water flow rate and fresh air percent. Due to the complexity and nonlinearity of AHU model and also the existence of various operating points and uncertainty, model uncertainties are included.... 

A new design for heat pump integrated humidification-dehumidification (HDH-HP) desalination cycles was proposed in the current experimental study. An evaporative condenser was designed and fabricated instead of a separate humidifier, heater, and air/water-cooled condensers find in previous HDH-HP systems. Meanwhile, the air dehumidification process in this work directly occurred inside the heat pump evaporator. The effect of several operating parameters such as ambient wet-bulb temperature, spraying saline water and airflow rates, compressor speed, superheat, and evaporator saturation temperature control modes of the electronic expansion valve (EEV) on freshwater production and GOR were... 

Over the past decades, drastic growth in the installed capacity of seawater desalination systems has increased the energy consumption and brine discharge to the environment. However, using renewable energies and zero liquid discharge systems for minimizing these challenges is limited due to the higher fresh water cost of the systems rather than that of the conventional systems. In this research, a bubble-column humidification-dehumidification zero liquid discharge system is coupled with a multiple-effect distillation/vapor compression system in a novel way to overcome the high water cost of conventional zero liquid discharge systems. Further, the base system and the solar-powered system is... 

Using zero liquid discharge systems is one of the efficient methods to reduce the negative environmental impact of the brines of the desalination systems and also to recycle the industrial wastewaters for reuse. Due to the simple fabrication process, low maintenance cost, intensive to inlet water quality, and the ability to use renewable and low-grade-heat, modified humidification-dehumidification systems may be a proper choice for the zero liquid discharge applications. Thus, in the present study, the energy, exergy, exergoeconomic, and exergoenvironmental assessment of three advanced brine recycle humidification-dehumidification systems for zero liquid discharge operation are... 

Among different types of geothermal processing used in the energy conversion systems, flash-binary geothermal can be the best scenario for high-temperature geothermal sources. Reviewing the available literature it can be found that the flash-binary geothermal power plants have a great potential to be extended to trigeneration systems, nonetheless they have received less attention. In this regard, a new trigeneration system for freshwater, power, and cooling production is devised using a flash-binary geothermal heat source at 170°C. In this devised trigeneration system, a humidification-dehumidification (HDH) unit is used as a binary cycle. Another merit of the devised trigeneration system is...