Sara Sultan
@utk.edu
Graduate Research Assistant
University of Tennessee
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Sara Sultan, Jason Hirschey, Navin Kumar, Borui Cui, Xiaobing Liu, Tim J. LaClair, and Kyle R. Gluesenkamp
MDPI AG
Phase change material (PCM)-based thermal energy storage (TES) can provide energy and cost savings and peak demand reduction benefits for grid-interactive residential buildings. Researchers established that these benefits vary greatly depending on the PCM phase change temperature (PCT), total TES storage capacity, system configuration and location and climate of the building. In this study, preliminary techno-economic performance is reported for a novel heat pump (HP)-integrated TES system using an idealized approach. A simplified HP-TES was modeled for 1 year of space heating and cooling loads for a residential building in three different climates in the United States. The vapor compression system of the HP was modified to integrate with TES, and all heat transfer to and from the TES was mediated by the HP. A single PCM was used for heating and cooling, and the PCT and TES capacity were varied to observe their effects on the building’s energy consumption, peak load shifting and cost savings. The maximum reduction in electric consumption, utility cost and peak electric demand were achieved at a PCT of 30 °C for New York City and 20 °C for Houston and Birmingham. Peak energy consumption in Houston, New York City, and Birmingham was reduced by 47%, 53%, and 70%, respectively, by shifting peak load using a time-of-use utility schedule. TES with 170 MJ storage capacity allowed for maximum demand shift from on-peak to off-peak hours, with diminishing returns once the TES capacity equaled the daily building thermal loads experienced during the most extreme ambient conditions.
Monojoy Goswami, Navin Kumar, Yuzhan Li, Jason Hirschey, Tim J. LaClair, Damilola O. Akamo, Sara Sultan, Orlando Rios, Kyle R. Gluesenkamp, and Samuel Graham
AIP Publishing
Salt hydrate-based phase-change materials are considered promising for future heat storage applications in residential heating/cooling systems. Smooth phase transition from the liquid to solid phase and vice versa is essential for effective heat exchanger; however, supercooling in salt hydrates delays the onset of liquid–solid phase transition. We investigate the molecular level mechanism of supercooling in sodium sulfate decahydrate (SSD). SSD is a complex salt hydrate whose properties are governed by electrostatic forces that include pure Coulombic interactions as well as hydrogen bonds. Experimentally, we examine the importance of a nucleator in reducing supercooling temperatures. We investigated the effect of various mass concentrations of a borax nucleator on a decrease of supercooling temperatures. Molecular dynamics simulation techniques are used to obtain a basic understanding of supercooling in SSD. We observe that by introducing borax as a nucleator, there is a decrease in the supercooling temperature before nucleation. Our molecular dynamics simulations show that long-range electrostatics between sodium and sulfate ion pairs and that with polar water molecules is responsible for delayed nucleation in SSD that results in supercooling, and also, dynamics of charged molecules slows down. The lack of crystallization leads to amorphous structures in supercooled SSD.
Ibadullah Safdar, Sara Sultan, Hamza Ahmad Raza, Muhammad Umer, and Majid Ali
Elsevier BV
Hamza Ahmad Raza, Sara Sultan, Shomaz ul Haq, Abid Hussain, Abdul Kashif Janjua, and Abeer Bashir
IEEE
This paper presents an economic, cost effective model of solar thermal tower power plant. In Solar Thermal Tower Power Plant heliostats are most expensive component and take 40 percent cost of overall power plant which is unenviable. In this work main focus was to find the minimum number of heliostats required to generate 1 MW of electricity by changing the flow rate, temperature and pressure of heat transfer fluid and steam. Effect of changing the flow rate on heliostats is discussed. For optimum placement of reflecting mirrors and solar receiver height, System Advisory Model is used. It was found that minimum 62 heliostats are required for 13000 kg/h steam flow rate. Further reduction in heliostats resulted in decreased steam flow rate which is limited by turbine input parameters. Solar radiation data for 26 July was taken from the Meteorological High Precision station installed in National University of Sciences and Technology, Islamabad Pakistan.
Hamza Ahmad Raza, Sara Sultan, Shomaz-Ul-Haq, and Majid Ali
IEEE
This paper presents an efficient solar water desalination system for the climate condition of Pakistan. Water scarcity issue of Pakistan is addressed and model of solar energy-based water desalination system is presented using TRNSYS software. Weather data profile of Karachi is taken in TRNSYS. Flat plate collector of 3 m2 is used to produce 3.249 kg/h clean water with steady state moisture rate to humidifier. It is observed that productivity of clean water is increased using parabolic mirror. It is found that temperature is increased using the same receiver area with parabolic trough and water production is increased from 3.249 to 3.276 kg/h for this system keeping the input moisture rate and air flow rate constant for both cases.
Hamza Ahmad Raza, Muhammad Asad, Sara Sultan, Shomaz-Ul-Haq, Nadia Shehzad, and Majid Ali
IEEE
This paper presents a simulation based approach to analyze the effect of solar concentrator's reflectivity on initial cost of the solar thermal tower power plant (STTPP). It discusses the reflectivity of different materials used as solar concentrators in STTPP. TRNSYS software is used to simulate the power plant and effect of using different reflective material is observed. It is found that with 0.9 reflectivity of solar mirror, 10300 heliostats are required to produce 40 MW of electricity which cost 13000 Million PKR while a small increase in the reflectance from 0.9 to 0.94 has decrease the cost to 11292 Million PKR. RETScreen software is used for cost analysis of this system. It is observed that 5.4 percent of the initial cost is reduced and payback period is decreased from 13 to 9 years.
Shomaz Ul Haq, Hamza Ahmad Raza, Ibadullah Safdar, Sara Sultan, Sufyan Naeem, and Majid Ali
IEEE
Heat transfer forms the basis of conversion of one form of energy to another. Increasing heat transfer area by using conventional methods of geometry design can increase the output temperature but this leads to a bulky and costly thermal system. Passive techniques can decrease the cost. The research presented revolves around enhancement of heat transfer using nanofluids. Nanofluids are colloidal suspensions of nanoparticles in a base fluid (thermal fluids) such as water with excellent thermal characteristics. They enhance heat transfer by increasing the convective heat transfer and thermal conductivity of nanofluid as compared to base fluid by increasing heat transfer area. An analysis of hydrodynamically and thermally developing or simultaneously developing laminar forced convection of nanofluids in circular pipes subjected to a constant wall heat flux boundary condition has been performed by numerical method. The numerical analysis was conducted using parametric three dimensional (3D) computational fluid dynamics (CFD) simulation code ANSYS CFX. Alumina (Al2O3) and copper oxide (CuO) nanoparticles were employed in water as base fluid in a liquid single-phase constant thermophysical properties model. The effect of design factors of concentration, diameter, Reynold (Re) number, and type of nanofluid on heat transfer coefficient (h), Nusselt (Nu) number, and pressure drop (ΔΡ) is investigated for different axial locations. Results reveal that increasing particle concentration from 1% to 5% increases the heat transfer coefficient for Al2O3-water by more than 5% similar to that by Re number. CuO shows little heat transfer enhancement due to high density and low thermal conductivity. Velocity increases along the length of the pipe. Moreover, the results were validated with empirical/theoretical and experimental correlations and agreed with an error less than 5%.
Sara Sultan, Majid Ali, Adeel Waqas, Hamza Ahmed Raza, Saba Aziz, and Shomaz-ul- Haq
IEEE
The overall broad purpose of this paper is to develop and evaluate a small scale solar humidification dehumidification water desalination system using a graphical tool TRNSYS and assess its thermal behavior. Considering the intense need for the development of alternate technologies for energy deficient and impoverished countries of the world like Pakistan, this model is in particular anticipated for underprivileged communities where pure and uncontaminated drinking water as well as modern technologies are not accessible. The system consists of isolated components for heating, evaporation and condensation, in order to lower the thermal losses. The weather file used was in standard TMY 2 format for Asian data. A flat plate solar collector, humidifier and dehumidifier are to be integrated in an open air open water configuration. The simulations for a water heated cycle revealed that the output water temperature be reliant strongly on the incident solar radiations and inlet water temperature. Collector area and inlet water flow rate also had a considerable impact on productivity. A significant increase in efficiency was observed by using a water storage tank and pre heating the feed water favorably influenced the output.