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Transient performance analysis and investigation of three proposed solar powered humidification–dehumidification (HDH) water desalination systems: single stage (SS), double stages (DS) and modified double stages (MDS) systems are presented for hot and humid cities. Open/closed modes of operations of the systems are also investigated. A parametric study of the hourly and daily systems performance is presented at various operating parameters. The results reveal that: (i) inserting solar collectors in HDH systems for air and water heating substantially enhances the system’s performance; (ii) the fresh water productivity of all systems at open mode of operation increases with increasing the outdoor air temperature and humidity; (iv) at low outdoor humidity, the system’s performance at closed mode of operation is higher than those at open mode of operation and the opposite is true at high outdoor humidity; (v) comparing between the three systems, MDS system (open mode) can produce fresh water of 350 kg/day with GORday of 1.63 and its fresh water productivity enhances with 86.7% and 34% than SS and DS systems, respectively; and (vi) using control system, the performance of the proposed systems can be maximized by changing between the open/closed mode of operations according to the outdoor conditions.

Modeling and performance study of large parabolic trough solar power plant using molten slat storage tank is conducted and presented for three different locations in Egypt (Aswan, Al-Arish and Hurghada) using 16 h storage system. The simulation algorithm and solar modeling have been created and simulated by MATLAB/SIMULINK program. A comparison between studied cities is introduced to select the best location for constructing the solar plant based on selection criteria; hot header outlet temperature, volume (hot and cold) variations during charging and discharging, and cycle power efficiency. A full design of the thermal power plant with the storage tanks is also conducted using a molten salt (60% NaNO3 and 40% KNO3). Moreover, hourly electricity plant output to obtain the influence of the thermal storage tank on the plant performance was calculated and presented. The results indicated that Aswan city is the optimum location to construct a 500 MW solar power plant under the Egyptian climate. A comparison for current model validation between simulated results and the actual results of existing plant (Archimede) was fulfilled and good agreement was obtained by maximum error 5%.

Compactness with high performance heat exchangers are main challenges in a lot of engineering applications. Thus, this research reports CFD simulation of a novel MTTHC (multi tubes in tube helically coiled) heat exchanger using ANSYS-FLUENT 14.5. The aim of the work is to investigate the thermal and hydraulic performance of the MTTHC for turbulent flow. The effects of the operating and geometrical parameters of the coil on the cold/hot water Nusselt numbers, heat transfer coefficients, pumping power, effectiveness, and thermal-hydraulic index are studied and presented. The results show that, the largest heat transfer coefficient is found at N = 3 and β = 0° & 90°, and the pumping power (P) rises with ≅ 20 times if N changed from 1 to 5 at any β. Moreover, the effectiveness of the coil (e) has the largest values at β = 0° & 90° and N=3, and it enhances with 8.5%, 9% and 7% if N increased from 1 to 3 at β = 0°, 45° and 90°, respectively. In addition, thermal-hydraulic index (ξ) improves with 5%, 8% and 6% if N increased from 1, to 3 at β = 0°, 45° and 90°, respectively. Finally, Numerical correlations for P, e and ξ are correlated and presented within reasonable errors.

Heat transfer characteristics and performances of a multi tubes in tube helically coiled (MTTHC) heat exchanger are numerically investigated. The effects of operating and geometrical parameters on the thermal and hydrodynamic performances of the coil are studied and presented for turbulent flow regimes. The current simulation model is compared and validated with available experimental results and a good agreement is obtained. The numerical results showed that, the overall heat transfer coefficient (Uo) enhanced by 23% and 28% with increasing Reynolds numbers of hot and cold water (Rehw and Recw) from 9000 to17000 and 14,000 to 22,000, respectively. Coil effectiveness (e) increased by 28% and 60% with increasing coil diameter (Dc) from 100–150 mm and 100 to 250 mm, respectively and increased with 20% with increasing the number of inner tubes (N) from 1 to 5. Moreover, the maximum values of the thermal-hydrodynamic performance index and coil effectiveness occurs at N = 3. The coil pitch has slight effect on the coil performance. Comparisons between the presented MTTHC with concentric tube in tube helically coiled (CTTHC) and multi tubes in straight tube (MTST) heat exchangers are conducted and showed that MTTHC heat exchangers displayed higher thermal performance. General numerical correlations for thermal and hydraulic coil performance are developed within acceptable errors.

In the present study, a CFD analysis using ANSYS-FLUENT 14.5 CFD package is used to investigate the characteristics of heat transfer of laminar flow in annulus formed by multi tubes in tube helically coiled heat exchanger. The numerical results are validated by comparison with previous experimental data and fair agreements were existed. The influences of the design and operation parameters such as heat flux, Reynolds numbers and annulus geometry on the heat transfer characteristics are investigated. Different annulus of different numbers of inner tubes, specifically 1, 2, 3, 4 and 5 tubes, are tested. The Results showed that for all the studied annulus, the heat flux has no effect on the Nusselt number and compactness parameter. The annulus formed by using five inner tubes showed the best heat transfer performance and compactness parameter. Correlation of predicting Nusselt number in terms of Reynolds number and number of inner tubes are presented.

A low energy HDH (humidification-dehumidification) and AC (air-conditioning) hybrid system using an efficient design of dehumidifier (strips-finned helical coil) and packing pad material (cellulose paper in bee-hive structure) is proposed. An experimental investigation of the performance of the proposed system is conducted for wide ranges of air and water flow rates and temperatures and packing pad thickness. The results showed that (i) the proposed hybrid system can produce fresh water and remove space cooling load to maintain the required comfort conditions, (ii) the fresh water production rate, cooling load capacity and the system performance increase with increasing air and water flow rates and temperatures and cooling pad thickness, (iii) the proposed HDH system with the new humidification-dehumidification sections has better productivity and performance compared to other systems, (vi) daily production cost of the system increases with increasing inlet air and water flow rates and decreasing cooling pad thickness and air and water temperatures, and (v) production cost per kg of fresh water decreases by increasing cooling pad thickness and air and water flow rates and temperatures. The system performance parameters (fresh water productivity, cooling load capacity, space supply air temperature and coefficient of performance) can reach to 17.42 kg/h, 3.9 kW and 16 °C, and 4.35, respectively. Moreover, the lowest specific cost of fresh water production can be obtained is 0.7 ¢/kgFW, respectively. Finally, empirical correlations of system productivities and performance parameters in terms of operating conditions and system geometric parameters were predicted within acceptable errors.

Theoretical investigation on the performance of a proposed innovated solar integrated system for air conditioning (A/C) and humidification dehumidification (HDH) water desalination in hot and humid regions is presented. Transient analysis and parametrical study for the system are conducted under different operating and design conditions. System performance parameters (fresh water production rate, cooling capacity, electrical power consumption, water recovery and system coefficient of performance) are hourly estimated and daily integrated for different operational and design conditions. The results reveal the increase of fresh water productivity, system water recovery, cooling capacity, electrical power consumption and COP of the system with the increase of air temperature, air humidity, and solar collectors area. For system assessment, the system performance parameters are compared with the performance of a basic system under the same conditions. Cost saving analysis showed the proposed system operates more economically and efficiently that in hot and humid climatic areas. General numerical correlations for system performance parameters are proposed in terms of the design and operational conditions.

A 3D-CFD investigation of airflow, temperature distribution and thermal comfort in high rise ceiling theaters air conditioned with underfloor air distribution (UFAD) system is presented for different operating and geometric conditions. Numerical simulations are implemented, using a commercial CFD package (Fluent 6.3), to understand the effects of supply air temperature, supply air velocity, space height and number of supply air diffusers on the performance of the air conditioning system and thermal comfort. For UFAD system evaluation, the traditional overhead mixing air distribution (OHAD) system are also modelled and compared with the UFAD system. The results showed that (i) the used numerical technique could accurately predict the airflow and temperature distribution in the high rise conditioned space, (ii) UFAD system is capable of creating smaller vertical variations of air temperature and a more comfortable environment and energy saving than OHAD system, (iii) the supply air velocity and temperature, number of diffusers and height of the space have a significant impact on thermal comfort, (iv) the optimum system performance and thermal comfort obtained at 18 °C supply air temperature, 0.8 m/s supply air velocity and proper numbers and distributions of supply diffusers, (v) the percentage of energy saving due to using UFAD system increases with increasing the theater height. The simulation results are validated with the available experimental data and good agreement are obtained.

Flow field and mixing characteristics of coolant radial jets injected radially from multiple nozzles rows of centreline distributer into a heated non-reacting crossflow in a cylindrical chamber is numerically investigated. The study simulates the process of air jets injection in the combustion chambers of gas turbines through discrete holes. Three-dimensional model using ANSYS-FLUENT 14.5 CFD package is used. The effects of jet-mixing ratio, nozzles diameter, distributer diameter, number of nozzles rows, number of nozzles per row on the penetration depth and mixing quality through chamber cross section are parametrically studied. The results are validated with the available experimental data and good agreement are obtained. The results showed that nozzle diameter, distributer diameter and jet-mixing ratio have effects on the penetration depth and the mixing quality compared to the effects of the number of nozzles per row and the number of nozzles rows. The effects are remarkable at high mixing ratio. The integral mixing quality along the chamber cross section increased with increasing mixing ratio, nozzles diameters, number of nozzles per row and number of nozzles rows. Dimensionless correlations for predicting the penetration depth and mixing quality in terms of the controlling parameters are developed.

Parametric and economic studies of the performance of a solar hybrid air conditioning (A/C) and humidification–dehumidification (HDH) water desalination system are presented. The system is integrated with thermal storage and auxiliary heating systems for steady-state operation. Fresh water production rate, fresh water recovery, cooling capacity, electrical power consumption, coefficient of performance and system economical index are studied at different operating and design parameters. The results show that (i) the electrical consumption of the auxiliary heater decreases with decreasing outdoor air flow rate and increasing both of outdoor air temperature, outdoor air humidity and temperature difference across the heating system, (ii) the increase in outdoor air temperature, outdoor humidity and temperature difference across the heating system increase the fresh water production and recovery rates, cooling capacity and the electric power consumption of the proposed system. Comparison with a basic air conditioning system showed that the proposed system has higher water production, cooling capacity, coefficient of performance (COP) and lower power/electricity consumptions at hot and humid regions. A cost analysis reveals that the saving in the total operating cost increases with increasing outdoor air temperature, and outdoor humidity and decreases with increasing temperature difference across the heating system.

Numerical simulations using computational fluid dynamics (CFD) are performed to investigate the flame length characteristics in rotary kilns using probability density function (PDF) approach. A commercial CFD package (ANSYS-Fluent) is employed for this objective. A 2-D axisymmetric model is applied to study the effect of both operating and geometric parameters of rotary kiln on the characteristics of the flame length. Three types of gaseous fuel are used in the present work; methane (CH4), carbon monoxide (CO) and biogas (50 % CH4 + 50 % CO2). Preliminary comparison study of 2-D modeling outputs of free jet flames with available experimental data is carried out to choose and validate the proper turbulence model for the present numerical simulations. The results showed that the excess air number, diameter of kiln air entrance, radiation modeling consideration and fuel type have remarkable effects on the flame length characteristics. Numerical correlations for the rotary kiln flame length are presented in terms of the studied kiln operating and geometric parameters within acceptable error.

In hot and dry climatic zones, direct evaporative cooling (DEC) system is used as an economical and efficient alternative to traditional air conditioning systems. The present paper concerns comprehensive experimental investigations and analysis of heat and mass transfer characteristics and thermal performance parameters of a bee-hive construction of corrugated-cellulose papers as a new cooling pad material. The performance parameters used to evaluate the effectiveness of the cooling pad materials are the outlet air temperature and relative humidity, pressure drop, humidifier effectiveness, rate of the evaporated water, sensible cooling capacity, specific cooling capacity (SCC), coefficient of performance (COP), specific water consumption (SWC), and Nusselt and Sherwood numbers. The cooling pad performance was investigated for a wide range of air and water temperatures and flow rates and pad thicknesses. The results show the enhancements of heat and mass transfer coefficients and the performance parameters with rising air temperature and water flow rate to humidifier. High values of the performance parameters (hc = 45 W/m2 oC and hm = 0.23 m/s, e h u m = 0.85 and COP = 170) are obtained compared to the traditional pad materials. Experimental correlations for the evaporative cooler performance parameters in terms of air and water temperatures and flow rates pad thicknesses are presented.

Vapor generated during rewetting/quenching of hot vertical surfaces/tubes by a falling liquid film forms countercurrent flow to the quench front propagation. This vapor in addition to the possibly rising vapors from other sources resist the downward propagation of the quench front and may cause partially or complete flooding of the injected liquid. The present work develops a semi analytical model to parametrically study the rewetting/quenching rate of a hot vertical tube by a falling liquid film in terms of initial tube temperature, flow rate of rising vapors, tube thickness and cooling water injection and penetration rates. Momentum, energy and conduction-controlled equations are used to find the model governing equations. Correlations for liquid penetration rate and interfacial friction factor driven from experimental data were incorporated in the model. The resulting governing equations were solved iteratively to study the effects of the controlling parameters on the quench front propagation velocity. Conditions of onset of flooding and complete flooding in terms of the controlling parameters are deduced and discussed. Results are compared with available experimental results and good agreement was obtained.

Performance of integrative air-conditioning (A/C) and humidification–dehumidification desalination systems proposed for hot and dry climatic regions is theoretically investigated. The proposed systems aim to energy saving and systems utilization in fresh water production. Four systems with evaporative cooler and heat recovery units located at different locations are proposed, analyzed and evaluated at different operating parameters (fresh air ratio, supply air temperature and outside air wet bulb temperature). Other two basic systems are used as reference systems in proposed systems assessment. Fresh water production rate, A/C cooling capacity, A/C electrical power consumption, saving in power consumptions and total cost saving (TCS) parameters are used for systems evaluations and comparisons. The results show that (i) the fresh water production rates of the proposed systems increase with increasing fresh air ratio, supply air temperature and outdoor wet bulb temperature, (ii) powers saving of the proposed systems increase with increasing fresh air ratio and supply air temperature and decreasing of the outdoor air wet bulb temperature, (iii) locating the evaporative cooling after the fresh air mixing remarkably increases water production rate, and (vi) incorporating heat recovery in the air conditioning systems with evaporative cooling may adversely affect both of the water production rate and the total cost saving of the system. Comparison study has been presented to identify systems configurations that have the highest fresh water production rate, highest power saving and highest total cost saving. Numerical correlations for fresh water production rate and total system energy consumption are developed and presented in terms of the controlling parameters.

The condensation process of water vapor from moist air flowing around horizontal pipe is investigated theoretically and experimentally. This process involved in many engineering applications, such as refrigeration and air conditioning. In the theoretical analysis, the flow is assumed to be laminar, steady and with constant physical properties. The condensation process is described by continuity, momentum, energy and mass in the form of dimensionless ordinary differential equations using similarity variables. The dimensionless governing equations are solved by Runge Kutta fourth order integration technique accompanied with shooting method. The boundary layer thickness of mass, thermal and hydrodynamic, in addition to Nusselt and Sherwood numbers are investigated at different Reynolds numbers, and condensation and position parameters. In the experimental work, the effects of air inlet conditions (i.e. relative humidity, and mass flow rate) are varied and examined on the condensation process. The findings show that the average heat and mass transfer coefficients increase with increasing air mass flow rate and air relative humidity, and decrease with increasing the temperature difference between the air dew point and pipe surface temperature. Comparisons between the present theoretical and experimental work with previous theoretical study are accomplished within accepted error.

CFD (computational fluid dynamics) simulation using a commercial package (Fluent-ANSYS) on industrial rotary kilns using annulus-type burners and methane gas was carried out to examine the characteristics of the flame length and flow visualization. New influencing design and operating parameters&mdash, primary air swirl number, primary air inlet annulus diameter, and secondary air temperature&mdash, were investigated and discussed. The influence of these parameters on axial temperature distribution, axial mean mixture fractions, velocity vectors, mixture fractions, and temperature contours were investigated. The current numerical findings were compared with existing experimental results to validate the simulation approach. The results showed that the primary air swirl number had a remarkable influence on the flame length at a lower primary air inlet annulus diameter ratio of 2.3. Moreover, the flame length increased by 20% and 6% with increasing the swirl number from zero to one for primary air inlet annulus diameter ratios of 2.3 and 5, respectively, and it also increased by 19% with increasing primary air inlet annulus diameter ratio from 2.3 to 5.

In the present study, computational fluid dynamics (CFD) methodology is used to investigate the confined non-premixed jet flames in rotary kilns. Simulations are performed using ANSYS-Fluent, a commercial CFD package. A two-dimensional axisymmetric model is conducted to understand the main operational and geometrical parameters of rotary kilns, which affect the flame behaviors, including the aerodynamics and heat transfer. Three kinds of fuels are employed in this study; Methane (CH4), Carbon Monoxide (CO) and Biogas (50% CH4 and 50% CO2). Confined jet flame length correlations are developed and presented in terms of kiln operational and geometrical parameters. Previous 2-D simulation results of free jet flames are used to select and validate the turbulence model, which applied in this study. The present simulation results are compared with available experimental data and previous analytical results, which show satisfactory agreement.

The accurate techniques of heating loads calculations are essential pace for equipment selection, system sizing and system design. With the help of getting the accurate data of heating loads and seasonal heating demands, the energy sources design for buildings become more effective. The present study highlights the dependence of heating loads values on the thermal properties of buildings envelopes; hence, a modified method of calculating the heating loads values and seasonal heating demands of residential buildings is developed mathematically. The present results are compared with ASHRAE standards. The results show that the data obtained from the present method are more accurate and effective than compared results. Moreover, it proves that the duration of heating seasons for each building even in the same climatic conditions are different. The modified method will open a new horizon in the field of heating system to provide accurate calculations of heating loads for many applications.

In this paper a comprehensive experimental parametric study on the performance of a new evaporative cooling pad type made of cellulose papers in bee-hive structure is presented. Four different pad sizes of face area 0.335 × 0.390 m2 and thicknesses 35, 70, 105, and 140 mm are examined. The tests are carried out in a wind tunnel adapted with the evaporative cooling system. Experiments are conducted to evaluate the cooling pad performance parameters: air temperature drop, air humidity ratio raise, cooling capacity, water evaporation rate, saturation efficiency, pressure drop, energy efficiency, energy efficiency ratio, exergy efficiency and overall exergy efficiency. The effects of the cooling pad thickness and the operating conditions including air velocity, inlet air temperature, water flow rate, water temperature and cooling pad thickness on the performance parameters are investigated. The results show that, the saturation efficiency, exergy efficiency and overall exergy efficiency of the proposed pad enhance with increasing the pad thickness and water flow rate and their highest obtained values are 84%, 92% and 74%, respectively. The maximum pressure drop, temperature drop and cooling capacity obtained for this pad are 46 Pa, 18 °C and 6.26 kW, respectively. Moreover, the highest energy efficiency ratio is 281 obtained at 2 m/s air velocity. Finally, new dimensionless experimental correlations for predicting the system performance parameters in terms of various operating conditions and system size are presented.

Airside heat and mass transfer and fluid flow characteristics of a wavy-finned-tube direct expansion air coil under cooling and dehumidifying condition have been experimentally investigated. Experiments were carried out to study the effects of operating conditions such as: air temperature, air relative humidity, air face velocity, and evaporator pressure on the airside performance (cooling capacity, dehumidification capacity, pressure drop, and heat transfer coefficient) of the coil. Charts for coil wet conditions, partially wet or totally wet, were conducted to identify the coil wet conditions in terms of the operating conditions. Two techniques, enthalpy potential method and equivalent dry-bulb temperature method, were used to analyze the data and to deduce correlations for Colburn factors for the different coil wet conditions. Comparison between the correlations predictions of the two techniques was presented.