Refrigeration & Air Conditioning, Battery Thermal Management System, New & Renewable Energy Applications, Building Services Engineering.
11
Scopus Publications
115
Scholar Citations
7
Scholar h-index
5
Scholar i10-index
Scopus Publications
Experimental and numerical investigation of a bar-and-plate heat exchanger for enhanced latent thermal energy storage Waseem Raza, Marco Tancon, Emanuele Zanetti, Arianna Berto, Stefano Rossi, Marco Azzolin Journal of Energy Storage, 2026 Latent thermal energy storage (LTES) employing phase change materials (PCMs) offers a promising solution for thermal management in various applications, compensating for the intermittent and unstable characteristics of several thermal energy sources, such as solar energy. However, the inherently low thermal conductivity of PCMs hinders their heat transfer efficiency, resulting in extended charging and discharging times. This limitation can be addressed either by enhancing the thermal conductivity of the PCM or by optimizing the storage system geometry. In this study, two LTES configurations, finned and finless units based on bar-and-plate technology, were tested under different conditions of mass flow rate (100, 150, 200 kg h −1 ) and heat transfer fluid (HTF) inlet temperature (46, 49 , 52 °C), corresponding to temperature difference (∆ T thermal ) of 3, 6 and 9 °C. To the best of the authors' knowledge, the bar-and-plate technology has been only marginally addressed in the context of LTES systems, and no comprehensive experimental investigations are currently available in the literature. The PCM employed, a paraffin wax (RT42), has a melting temperature ra nge between 38.2 °C and 42.5 °C. Results demonstrated that the finned unit reduced the melting time by up to 84 % compared to the finless configuration. At ∆ T thermal = 9 °C and a mass flow rate of 200 kg h −1 , the charging process was completed within 2 hours for the finned unit versus about 8 hours for the finless unit. Moreover, for the finned unit, increasing ∆ T thermal from 3 °C to 9 °C resulted in a 28–50 % decrease in melting time, while an increase in the mass flow rate from 100 to 200 kg h −1 shortened melting time by about 35 %. As a further step, the experimental data were used to validate a resistance-capacitance numerical model of the LTES unit, providing a valuable tool for LTES optimization and design according to specific application requirements. Unlike other available calculation methods, the developed model accounts for the explicit incorporation of fin geometry and PCM material in equivalent conductivities (PCM-fin composite) to capture the directional heat transfer pathways. Moreover, a parametric study was carried out to analyze the effect of fin parameters on melting time and energy storage. • Two bar-and-plate thermal energy storage units are tested with paraffin RT42. • Fins allow to reduce charging time by four times compared to a finless unit. • Paraffin melting time depends on the heat transfer fluid flow rate and temperature. • A resistance-capacitance model of the finned unit is developed in Matlab®. • The model is validated with experimental data and used for a parametric study.
Enhancing thermal comfort: a comprehensive review of wearable cooling systems Waseem Raza, Arianna Berto, Marco Tancon, Lorenzo Moro, Marco Azzolin Next Materials, 2025 Exposure to hot environments can induce physiological thermal strain in the human body, leading to reduced working endurance, impaired performance, and an elevated risk of heat-related illnesses. Activities such as sports, military training, and physically demanding work like firefighting can worsen these conditions. The increasing demand for energy-efficient solutions and diverse application requirements has driven the development of wearable cooling systems. These systems offer a localized and efficient alternative to conditioning entire environments, especially for individuals working outdoors or in settings where traditional air conditioning is impractical. This review provides a comprehensive overview of wearable cooling systems, covering their operating principles, designs, testing methodologies, applications, benefits, challenges, and classifications. Wearable cooling systems have been categorized into active, passive, and hybrid types, employing various cooling mechanisms, including air cooling, liquid cooling, vapor-compression cycle cooling, thermoelectric cooling, gas cooling, vacuum desiccant cooling, evaporative cooling, phase change materials, and conductive and radiative textile-based cooling. The review assesses these technologies based on cooling capacity, weight, and operating time, offering a rationale for their selection. Additionally, insights into future research opportunities in wearable cooling systems are discussed, emphasizing the need for continued innovation to enhance thermal comfort and safety.
On the prediction and optimization of the flow boiling heat transfer in mini and micro channel heat sinks Uzair Sajjad, Waseem Raza, Imtiyaz Hussain, Muhammad Sultan, Hafiz Muhammad Ali, Najaf Rubab, Wei-Mon Yan Progress in Nuclear Energy, 2024 The most common methods for predicting flow boiling heat transfer in mini/micro channels-based heat sinks rely on semi-empirical correlations derived from experimental data. However, these correlations are often limited to specific testing conditions. This study proposes a novel approach using deep learning and genetic algorithms (GA) to predict and optimize refrigerants' flow boiling heat transfer coefficients (FBHTC) in mini/microchannels-based heat sinks. The dataset used in this study includes FBHTC observations from the literature for seven refrigerants (R1234yf, R1234ze, R134A, R513A, R410A, R22, and R32). The optimal input parameters identified include hydraulic diameters ranging from 1 to 7 mm, saturation temperature from 0 to 20 °C, flow qualities from 0.006 to 0.972, heat flux from 3 to 78.8 kW/m 2 , and mass fluxes between 100 and 1200 kg/m 2 s. Gradient-boost regression trees were employed to develop the deep learning and GA models for accurate estimation and optimization. Correlation analysis and feature engineering selected the most influential parameters to construct a precise and simple model. The results demonstrate that the models could estimate refrigerants' FBHTC with high accuracy, achieving an R 2 of 0.988 and a mean squared error (MSE) of 0.05%. The GA-based method effectively optimized the FBHTC for each refrigerant by determining the appropriate input parameters, including the saturation temperature, heat and mass fluxes, quality, and hydraulic diameter. Additionally, a parametric analysis using explainable artificial intelligence was conducted to interpret the impact of each input parameter on the FBHTC.
A physics-informed, data-driven framework for estimation and optimization of two-phase pressure drop of refrigerants in mini- and macro channels Imtiyaz Hussain, Waseem Raza, Uzair Sajjad, Naseem Abbas, Hafiz Muhammad Ali, Khalid Hamid, Wei-Mon Yan Results in Engineering, 2024 At present, there is no universally accepted approach for forecasting the flow boiling heat transfer in the scientific literature. The objective of this study is to predict and optimize the two-phase pressure drop (2ϕΔP) for different refrigerants in both mini and macro-sized channels under various operating conditions. The dataset is amassed from open literature and consists of 1954 points that include seven different refrigerants, including R12345yf, R1234ze, R134A, R410A, R22, R744, and R717 containing heat flux (Q) in the range 0–40 kW/m2, hydraulic diameters (Dh) in the range 0.509–14 mm, mass flux in the range 55 < G < 1800 kg/m2s, saturation temperature (Tsat) in the range -40 – 43 °C, and flow qualities (x) in the range 0.001–0959. The first step involves conducting feature engineering operations to select the most significant and impactful features for estimating the considered output. The interpretation by Pearson’s correlation highlighted that Dh, Tsat, x, Q, and G were the most impactful params. The Bayesian optimization incorporated with surrogacy was used to determine the required hyper-parameters, which were then deployed to form multi-layer deep neural network (DNN) for estimating 2ϕΔP. A metaheuristic algorithm known as differential evolution (GA) was used to estimate Dh, Tsat, x, Q, and G to minimize the pressure drop. The performance of the established model was determined to be highly accurate with an accuracy of 0.9985. Additionally, an appropriate 2ϕΔP value for each refrigerant was provided to obtain the optimized values of the different input features. The optimized ML (regression) models performed better than the existing semi-empirical pressure drop correlations. This approach can be beneficial for the development and improvement of various engineering systems, particularly those involving the 2ϕΔP of numerous refrigerants.
On the Critical Heat Flux Assessment of Micro- and Nanoscale Roughened Surfaces Uzair Sajjad, Imtiyaz Hussain, Waseem Raza, Muhammad Sultan, Ibrahim M. Alarifi, Chi-Chuan Wang Nanomaterials, 2022 The boiling crisis or critical heat flux (CHF) is a very critical constraint for any heat-flux-controlled boiling system. The existing methods (physical models and empirical correlations) offer a specific interpretation of the boiling phenomenon, as many of these correlations are considerably influenced by operational variables and surface morphologies. A generalized correlation is virtually unavailable. In this study, more physical mechanisms are incorporated to assess CHF of surfaces with micro- and nano-scale roughness subject to a wide range of operating conditions and working fluids. The CHF data is also correlated by using the Pearson, Kendal, and Spearman correlations to evaluate the association of various surface morphological features and thermophysical properties of the working fluid. Feature engineering is performed to better correlate the inputs with the desired output parameter. The random forest optimization (RF) is used to provide the optimal hyper-parameters to the proposed interpretable correlation and experimental data. Unlike the existing methods, the proposed method is able to incorporate more physical mechanisms and relevant parametric influences, thereby offering a more generalized and accurate prediction of CHF (R2 = 0.971, mean squared error = 0.0541, and mean absolute error = 0.185).
Capacity control of a vehicle air-conditioning system using pulse width modulated duty cycle compressor Gwang Soo Ko, Waseem Raza, Youn Cheol Park Case Studies in Thermal Engineering, 2021 The air conditioning system is the most significant auxiliary load on a vehicle where the compressor consumed the largest from the engine, leading to high fuel consumption. Depending upon nature, the variable-capacity compressor reduces cycling on/off. It delivers cooling/heating to a cabin without adjusting the engine rpm, offering superior part-load performance to improve comfort. Consequently, power consumption is growing as an increase in inefficiency. Additionally, systems with continuous compressor modulation can automatically change their energy consumption as required. The paper aims to save energy by reducing fuel consumption in the system. It is because this technology helps us to deduct energy consumption. The test facilities were designed to determine the system capacity with refrigerant side capacity measurement with a mass flow rate of the refrigerant and enthalpy difference across the evaporator. R-134a is considered a refrigerant in this system. Pulse width modulation (PWM) with a duty cycle is used as a command controller or method of reducing power by pulsing its electrical current by effectively chopping it into discrete parts to control the capacity. The results demonstrate that a system consumed 1.2 kW power at 900 rpm, having 4 kW of the capacity. The system also utilized 2 kW power at 2500 rpm with 4.6 kW capacity, which directs the slight increase in power consumption with a significant increase in capacity. Systems with continuous compressor modulation automatically adjust their energy consumption according to the needs of the application. By using air conditioning with this technology vehicles, the owner can reduce energy consumption.
A Study on the Combined Driven Refrigeration Cycle Using Ejector Waseem Raza, Gwang Soo Ko, Youn Cheol Park International Journal of Air Conditioning and Refrigeration, 2021 The rising need for thermal comfort has resulted in a rapid increase in refrigeration systems’ usage and, subsequently, the need for electricity for air-conditioning systems. The ejector system can be driven by a free or affordable low-temperature heat source such as waste heat as the primary source of energy instead of electricity. Heat-driven ejector refrigeration systems become a promising solution for reducing energy consumption to conventional compressor-based refrigeration technologies. An air-conditioning system that uses the ejector achieves better performance in terms of energy-saving. This paper presents a study on the combined driven refrigeration cycle based on ejectors to maximize cycle performance. The experimental setup is designed to determine the coefficient of performance (COP) with ejector nozzle sizes 1.8, 3.6, and 5.4[Formula: see text]mm, respectively. In this system, the R-134a refrigerant is considered as a working fluid. The results depict that the efficiency is higher than that of the conventional refrigeration method due to comparing the performance of the conventional refrigeration cycle and the combined driven refrigeration cycle. The modified cycle efficiency is better than the vapor compression cycle below 0∘C, which implies sustainability at low temperatures by using low-grade thermal energy. For the improvement of mechanical efficiency, proposed cycle can be easily used.
Induction heater based battery thermal management system for electric vehicles Waseem Raza, Gwang Soo Ko, Youn Cheol Park Energies, 2020 The life and efficiency of electric vehicle batteries are susceptible to temperature. The impact of cold climate dramatically decreases battery life, while at the same time increasing internal impedance. Thus, a battery thermal management system (BTMS) is vital to heat and maintain temperature range if the electric vehicle’s batteries are operating in a cold climate. This paper presents an induction heater-based battery thermal management system that aims to ensure thermal safety and prolong the life cycle of Lithium-ion batteries (Li-Bs). This study used a standard simulation tool known as GT-Suite to simulate the behavior of the proposed BTMS. For the heat transfer, an indirect liquid heating method with variations in flow rate was considered between Lithium-ion batteries. The battery and cabin heating rate was analyzed using the induction heater powers of 2, 4, and 6 kW at ambient temperatures of −20, −10, and 0 °C. A water and ethylene glycol mixture with a ratio of 50:50 was considered as an operating fluid. The findings reveal that the thermal performance of the proposed system is generally increased by increasing the flow rate and affected by the induction heater capacity. It is evident that at −20 °C with 27 LPM and 6 kW heater capacity, the maximum heat transfer rate is 0.0661 °C/s, whereas the lowest is 0.0295 °C/s with 2 kW heater capacity. Furthermore, the proposed BTMS could be a practical approach and help to design the thermal system for electric vehicles in the future.
A parametric study of a solar-assisted house heating system with a seasonal underground thermal energy storage tank Le Minh Nhut, Waseem Raza, Youn Cheol Park Sustainability Switzerland, 2020 The requirement for energy is increasing worldwide as populations and economies develop. Reasons for this increase include global warming, climate change, an increase in electricity demand, and paucity of fossil fuels. Therefore, research in renewable energy technology has become a central topic in recent studies. In this study, a solar-assisted house heating system with a seasonal underground thermal energy storage tank is proposed based on the reference system to calculate the insulation thickness effect, the collector area, and an underground storage tank volume on the system performance according to real weather conditions at Jeju Island, South Korea. For this purpose, a mathematical model was established to calculate its operating performance. This mathematical model used the thermal response factor method to calculate the heat load and heat loss of the seasonal underground thermal energy storage tank. The results revealed that on days with different weather conditions, namely, clear weather, intermittent clouds sky, and overcast sky, the obtained solar fraction was 45.8%, 17.26%, and 0%, respectively. Using this method, we can save energy, space, and cost. This can then be applied to the solar-assisted house heating system in South Korea using the seasonal underground thermal energy storage tank.
Experimental and Numerical Analysis of Heat Transfer Enhancement in Latent Thermal Energy Storage Systems W Raza University of Padova , 2026 2026
Experimental and numerical investigation of a bar-and-plate heat exchanger for enhanced latent thermal energy storage W Raza, M Tancon, E Zanetti, A Berto, S Rossi, M Azzolin Journal of Energy Storage 141, 119064 , 2026 2026 Citations: 4
Comparative analysis of Lauric Acid and RT42 paraffin in a bar-and-plate heat exchanger W Raza, M Tancon, E Zanetti, A Berto, M Azzolin EXHFT-11, Beijing, China , 2025 2025
Enhancing thermal comfort: a comprehensive review of wearable cooling systems W Raza, A Berto, M Tancon, L Moro, M Azzolin Next Materials 8, 100762 , 2025 2025 Citations: 5
On the prediction and optimization of the flow boiling heat transfer in mini and micro channel heat sinks U Sajjad, W Raza, I Hussain, M Sultan, HM Ali, N Rubab, WM Yan Progress in Nuclear Energy 177, 105466 , 2024 2024 Citations: 20
A physics-informed, data-driven framework for estimation and optimization of two-phase pressure drop of refrigerants in mini-and macro channels I Hussain, W Raza, U Sajjad, N Abbas, HM Ali, K Hamid, WM Yan Results in Engineering 23, 102538 , 2024 2024 Citations: 7
Heat Transfer Enhancement in Latent Thermal Energy Storage Unit W Raza, A Berto, E Zanetti, M Azzolin, D Del Col 14th IIR Conference on Phase-Change Materials and Slurries, Paris, France , 2024 2024
Numerical analysis on performance characteristics of an ejector W Raza, GS Ko, YC Park 17th International Heat Transfer Conference, 2023, Cape Town, South Africa , 2023 2023
Comparative Analysis on Ejector and Converging Tee-driven Refrigeration Systems GS Ko, W Raza, YC Park 14th IEA Heat Pump Conference, 2023, Chicago, USA , 2023 2023
On the critical heat flux assessment of micro-and nanoscale roughened surfaces U Sajjad, I Hussain, W Raza, M Sultan, IM Alarifi, CC Wang Nanomaterials 12 (18), 3256 , 2022 2022 Citations: 21
Nanofluids for enhanced performance of building thermal energy systems N Abbas, MB Awan, MA Badshah, U Sajjad, W Raza Advances in Nanofluid Heat Transfer, 479-501 , 2022 2022 Citations: 8
Capacity Control of a Vehicle Air-Conditioning System using Pulse Width Modulated Duty Cycle Compressor GS Ko, W Raza, YC Park Case Studies in Thermal Engineering, 100986 , 2021 2021 Citations: 10
A Study on the Combined Driven Refrigeration Cycle Using Ejector W Raza, GS Ko, YC Park International Journal of Air-Conditioning and Refrigeration , 2021 2021 Citations: 2
Evaluation of Indirect Liquid Cooling for Electric Vehicle Battery Thermal Management System W Raza Graduate School of Jeju National University , 2021 2021 Citations: 1
Performance Comparison of a Water-to-Water Heat Pump System with Low GWP Refrigerant W Raza, O Tuul, BC Kim, YC Park Korean Society of Mechanical Engineers Conference, South Korea , 2020 2020
Induction Heater Based Battery Thermal Management System for Electric Vehicles W Raza, GS Ko, YC Park Energies 13 (21), 5711 , 2020 2020 Citations: 17
A Parametric Study of a Solar-Assisted House Heating System with a Seasonal Underground Thermal Energy Storage Tank LM Nhut, W Raza, YC Park Sustainability 12, 8686 , 2020 2020 Citations: 15
Performance Evaluation of Battery Thermal Management System in Electric Vehicle using Induction Heater (Part 1: Parallel System) W Raza, GS Ko, YC Park International Journal of Air-Conditioning and Refrigeration , 2020 2020 Citations: 5
Development of a Heat Pump System using Waste Heat from Power Plant W Raza, JH Kim, J Jang, T Otgonpurev, YC Park The 15th Symposium on Science and Technology, Nagasaki, Japan , 2020 2020
MOST CITED SCHOLAR PUBLICATIONS
On the critical heat flux assessment of micro-and nanoscale roughened surfaces U Sajjad, I Hussain, W Raza, M Sultan, IM Alarifi, CC Wang Nanomaterials 12 (18), 3256 , 2022 2022 Citations: 21
On the prediction and optimization of the flow boiling heat transfer in mini and micro channel heat sinks U Sajjad, W Raza, I Hussain, M Sultan, HM Ali, N Rubab, WM Yan Progress in Nuclear Energy 177, 105466 , 2024 2024 Citations: 20
Induction Heater Based Battery Thermal Management System for Electric Vehicles W Raza, GS Ko, YC Park Energies 13 (21), 5711 , 2020 2020 Citations: 17
A Parametric Study of a Solar-Assisted House Heating System with a Seasonal Underground Thermal Energy Storage Tank LM Nhut, W Raza, YC Park Sustainability 12, 8686 , 2020 2020 Citations: 15
Capacity Control of a Vehicle Air-Conditioning System using Pulse Width Modulated Duty Cycle Compressor GS Ko, W Raza, YC Park Case Studies in Thermal Engineering, 100986 , 2021 2021 Citations: 10
Nanofluids for enhanced performance of building thermal energy systems N Abbas, MB Awan, MA Badshah, U Sajjad, W Raza Advances in Nanofluid Heat Transfer, 479-501 , 2022 2022 Citations: 8
A physics-informed, data-driven framework for estimation and optimization of two-phase pressure drop of refrigerants in mini-and macro channels I Hussain, W Raza, U Sajjad, N Abbas, HM Ali, K Hamid, WM Yan Results in Engineering 23, 102538 , 2024 2024 Citations: 7
Enhancing thermal comfort: a comprehensive review of wearable cooling systems W Raza, A Berto, M Tancon, L Moro, M Azzolin Next Materials 8, 100762 , 2025 2025 Citations: 5
Performance Evaluation of Battery Thermal Management System in Electric Vehicle using Induction Heater (Part 1: Parallel System) W Raza, GS Ko, YC Park International Journal of Air-Conditioning and Refrigeration , 2020 2020 Citations: 5
Experimental and numerical investigation of a bar-and-plate heat exchanger for enhanced latent thermal energy storage W Raza, M Tancon, E Zanetti, A Berto, S Rossi, M Azzolin Journal of Energy Storage 141, 119064 , 2026 2026 Citations: 4
A Study on the Combined Driven Refrigeration Cycle Using Ejector W Raza, GS Ko, YC Park International Journal of Air-Conditioning and Refrigeration , 2021 2021 Citations: 2
Evaluation of Indirect Liquid Cooling for Electric Vehicle Battery Thermal Management System W Raza Graduate School of Jeju National University , 2021 2021 Citations: 1
Experimental and Numerical Analysis of Heat Transfer Enhancement in Latent Thermal Energy Storage Systems W Raza University of Padova , 2026 2026
Comparative analysis of Lauric Acid and RT42 paraffin in a bar-and-plate heat exchanger W Raza, M Tancon, E Zanetti, A Berto, M Azzolin EXHFT-11, Beijing, China , 2025 2025
Heat Transfer Enhancement in Latent Thermal Energy Storage Unit W Raza, A Berto, E Zanetti, M Azzolin, D Del Col 14th IIR Conference on Phase-Change Materials and Slurries, Paris, France , 2024 2024
Numerical analysis on performance characteristics of an ejector W Raza, GS Ko, YC Park 17th International Heat Transfer Conference, 2023, Cape Town, South Africa , 2023 2023
Comparative Analysis on Ejector and Converging Tee-driven Refrigeration Systems GS Ko, W Raza, YC Park 14th IEA Heat Pump Conference, 2023, Chicago, USA , 2023 2023
Performance Comparison of a Water-to-Water Heat Pump System with Low GWP Refrigerant W Raza, O Tuul, BC Kim, YC Park Korean Society of Mechanical Engineers Conference, South Korea , 2020 2020
Development of a Heat Pump System using Waste Heat from Power Plant W Raza, JH Kim, J Jang, T Otgonpurev, YC Park The 15th Symposium on Science and Technology, Nagasaki, Japan , 2020 2020
