Search Results (14)

Functional polymers are designed to enhance the evaporative cooling capacity of sports clothing ensembles, though little is known about how they alter the material properties of commonly used fabrics. The aim of this study was to quantify the impact of a commercially available textile finish treatment (HeiQ Smart Temp ^TM) on the structural, thermal, and moisture management properties of synthetic (SYN; 100% polyester) and blended (BLEND; 47% lyocell, 46% cotton, 7% elastane) fabrics. Structural (fabric mass, thickness, bulk density, relative porosity), thermal (air permeability, water vapour permeability, water vapour resistance) and moisture management properties (wetting time, spreading speed, wetting radius, absorption, vertical wicking rate) were assessed and compared between treated and untreated samples. Significant improvements (p < 0.05) in air permeability (SYN: Δ 26.0 mm.s⁻¹; BLEND: Δ 61.6 mm·s⁻¹), wetting time (SYN: Δ 0.3 s; BLEND: Δ 0.3 s), and spreading speed (BLEND: Δ 1.1 mm·s⁻¹; SYN: no change) were recorded following treatment. Non-significant changes in water vapour permeability (SYN: Δ 0.1; BLEND: Δ 0.1), water vapour resistance (SYN: Δ 0.7 Pa·m²W⁻¹; BLEND: Δ 0.4 Pa·m²W⁻¹) and vertical wicking (BLEND: Δ 6.1 mm·s⁻¹; SYN: no change) were also observed following treatment. Though not all material properties improved, this study provides evidence that the functional polymer treatment can enhance the evaporative cooling capacity of sports clothing fabrics. Future research is needed to understand how these results translate to physiological, perceptual, and performance-based effects in wearer trials during exercise. Full article

This study presents a comprehensive thermodynamic simulation and parametric analysis of a single-effect lithium bromide–water (LiBr–H₂O) vapour absorption refrigeration system (VARS) to assess the influence of key operating parameters on its performance, which is primarily measured by the coefficient of performance. The thermodynamic properties of the LiBr–H₂O solution are assessed using P-T-x diagrams to establish the operational limits of the cycle for given constraints, such as the absorber and the generator temperatures and the cycle’s operating pressures. The analysis includes the effects of generator temperature ($T_{gen}$), evaporator pressure ($P_{evap}$), and solution heat effectiveness ($\eta$) on the cycle performance. Additionally, exergy analyses of the cycle’s major components are performed. Simulation results demonstrate that $T_{gen}$ is the most dominant parameter that increases the COP non-linearly from 0.35 at 85 °C to 0.73 at 110 °C (for $\eta$ = 0.5, $T_{cond}$ = 40 °C), while the circulation ratio decreases sharply. Moreover, higher evaporator pressure positively influences the COP; for instance, increasing the evaporator pressure from 0.8 kPa to 1.2 kPa raised the COP from 0.71 to 0.76. This is directly correlated with the increased concentration difference between the strong and weak solutions. The heat recovery effectiveness proved vital for energy optimisation: increasing the recovery effectiveness from 0.5 to 0.9 improved the COP from approximately 0.72 to 0.82 at a fixed $T_{gen}$ of 100 °C. Absorber temperatures limit the minimum operating temperatures of the generator for the vapour production of the refrigerant (water). Moreover, the higher condenser/absorber temperatures significantly deteriorate the performance of the cycle; for instance, raising the operating temperature of the condenser/absorber from 40 °C to 45 °C results in the COP value dropping by up to 35% at a generator operating temperature of nearly 100 °C. Among all cycle components, the generator exhibits the highest exergy loss, especially at lower generator temperatures. These findings provide essential optimisation strategies for designing and operating solar or waste heat-driven LiBr–H₂O VARS units efficiently. Full article

The insufficiency of energy supply and availability remains a significant global energy challenge. This work proposes a novel approach to addressing global energy challenges by testing the supercritical property and conversion of low-temperature thermal heat into useful energy. It introduces a combined-cascade steam-to-steam trigeneration cycle integrated with vapour absorption refrigeration (VAR) and district heating systems. Energetic and exergetic techniques were applied to assess irreversibility and exergetic destruction. At a gas turbine power of 26.1 MW, energy and exergy efficiencies of 76.68% and 37.71% were achieved, respectively, while producing 17.98 MW of electricity from the steam-to-steam driven cascaded topping and bottoming plants. The cascaded plant attained an energetic efficiency of 38.45% and an exergy efficiency of 56.19%. The overall cycle efficiencies were 85.05% (energy) and 77.99% (exergy). More than 50% of the plant’s lost energy came from the combustion chamber of the gas turbine. The trigeneration system incorporated a binary NH₃–H₂O VAR system, emphasizing its significance in low-temperature energy systems. The VAR system achieved a cycle exergetic efficiency of 92.25% at a cooling capacity of 2.07 MW, utilizing recovered waste heat at 88 °C for district hot water. The recovered heat minimizes overall exergy destruction, enhancing thermal plant performance. Full article

The use of lime as a binder in hemp–lime considerably increases the drying time of hemp–lime after casting. Furthermore, lime is a non-renewable mineral resource. As such, this paper explores the effectiveness of using an alternative non-mineral binder instead of lime to formulate a novel hemp–shive insulation. The moisture-dependent thermal conductivity, adsorption isotherm, vapour diffusion resistance factor, and in-built hygrothermal performance of four variants of a novel bio-based insulation were investigated. The hygrothermal performance of the novel hemp–shive insulation was compared with that of a previously developed novel hemp–lime insulation. No significant variation in thermal conductivity of hemp–shive insulations between the equilibrium moisture contents (EMC) at 0% and 50% relative humidity (RH) was observed, but there was a substantial increase in thermal conductivity hemp–shive insulations when the material reached the EMC at 98% RH. The average dry thermal conductivity values of hemp–shive and hemp–lime insulations were also similar. The adsorption isotherms of hemp–shive insulations were determined at 0%, 20%, 50%, 70%, 90%, and 98% relative humidity steps. At 98% RH, the moisture adsorption capacity of hemp–shive insulations was 4-to-5-times higher than that of hemp–lime insulation. Hemp–shive insulations’ vapour diffusion resistance factor (µ value) was about double the µ value of hemp–lime insulation. Hemp–shive insulations exhibited 4-to-5-times higher water absorption resistance than that of hemp–lime insulation. Numerically determined porosity values of hemp–shive agree with the values of wood-based insulation materials of similar density. Finally, using all experimentally acquired data as inputs, dynamic whole-building hygrothermal simulations were carried out and the results show that novel hemp–shive insulation materials perform at a similar level to the hemp–lime insulation in terms of heating and cooling energy demand but require 45% less energy for humidification. However, the relative humidity inside the hemp–shive wall remains higher than 70%, which can potentially induce mould growth. Full article

The performance of a plate heat exchanger (PHE), in comparison with the conventional shell and tube types, through a trade-off analysis of energy cost and capital cost resulting from different temperature approaches in the cross-exchanger of a solvent-based CO₂ capture process, was evaluated. The aim was to examine the cost reduction and CO₂ emission reduction potentials of the different heat exchangers. Each specific heat exchanger type was assumed for the cross-exchanger, the lean amine cooler and the cooler to cool the direct contact cooler’s circulation water. The study was conducted for flue gases from a natural-gas combined-cycle power plant and the Brevik cement plant in Norway. The standard and the lean vapour compression CO₂ absorption configurations were used for the study. The PHE outperformed the fixed tube sheet shell and tube heat exchanger (FTS-STHX) and the other STHXs economically and in emissions reduction. The optimal minimum temperature approach for the PHE cases based on CO₂ avoided cost were achieved at 4 °C to 7 °C. This is where the energy consumption and indirect emissions are relatively low. The lean vapour compression CO₂ capture process with optimum PHE achieved a 16% reduction in CO₂ avoided cost in the cement plant process. When the available excess heat for the production of steam for 50% CO₂ capture was considered together with the optimum PHE case of the lean vapour compression process, a cost reduction of about 34% was estimated. That is compared to a standard capture process with FTS-STHX without consideration of the excess heat. This highlights the importance of the waste heat at the Norcem cement plant. This study recommends the use of plate heat exchangers for the cross-heat exchanger (at 4–7 °C), lean amine cooler and the DCC unit’s circulation water cooler. To achieve the best possible CO₂ capture process economically and in respect of emissions reduction, it is imperative to perform energy cost and capital cost trade-off analysis based on different minimum temperature approaches. Full article

Combined systems for power production and thermally activated cooling have a high potential for improving the efficiency and utilisation of thermal systems. In this regard, various configurations have been proposed and are comprehensively reviewed. They are primarily based on absorption systems and the implementation of multiple levels of complexity and flexibility. The configuration of the absorption power and cooling combined cycle proposed herein has wide commercial applicability owing to its simplicity. The configuration of the components is not new. However, the utilisation of aqueous salt solutions, the comparison with ammonia chiller and with absorption power cycles, the focus on parameters that are important for real-life applications, and the comparison of the performances for constant heat input and waste heat recovery are novel. The proposed cycle is also compared with a system based on the organic Rankine cycle and vapour compression cycle. An investigation of its performance proves that the system is suitable for a given range of boundary conditions from a thermodynamic standpoint, as well as in terms of system complexity and technical feasibility. New possibilities with regard to added power production have the potential to improve the economics and promote the use of absorption chiller systems. Full article

The food manufacturing sector is one of the most dominant consumers of energy across the globe. Food processing methods such as drying, baking, frying, malting, roasting, etc. rely heavily on the heat released from burning fossil fuels, mainly natural gas or propane. Less than half of this heat contributes to the actual processing of the product and the remaining is released to the surroundings as waste heat, primarily through exhaust gases at 150 to 250 °C. Recovering this waste heat can deliver significant fuel, cost and CO₂ savings. However, selecting an appropriate sink for this waste heat is challenging due to the relatively low source temperature. This study investigates a novel application of gas-to-air low temperature waste heat recovery technology for a confectionary manufacturing process, through a range of experiments. The recovered heat is used to preheat a baking oven’s combustion air at inlet before it enters the fuel-air mixture. The investigated technology is compared with other waste heat recovery schemes involving Regenerative Organic Rankine Cycles (RORC), Vapour Absorption Refrigeration (VAR) and hot water production. The findings indicate that utilising an oven’s exhaust gases to preheat combustion air can deliver up to 33% fuel savings, provided a sufficiently large heat sink in the form of oven combustion air is available. Due to a lower investment cost, the technology also offers a payback period of only 1.57 years, which makes it financially attractive when compared to others. The studied waste heat recovery technologies can deliver a CO₂ savings of 28–356 tonnes per year from a single manufacturing site. The modelling and comparison methodology, observations and outcomes of this study can be extended to a variety of low temperature food manufacturing processes. Full article

There is a burden of adequate energy supply for meeting demand and reducing emission to avoid the average global temperature of above 2 °C of the pre-industrial era. Therefore, this study presents the exergoeconomic and environmental analysis of a proposed integrated multi-generation plant (IMP), with supplemental biomass-based syngas firing. An in-service gas turbine plant, fired by natural gas, was retrofitted with a gas turbine (GT), steam turbine (ST), organic Rankine cycle (ORC) for cooling and power production, a modified Kalina cycle (KC) for power production and cooling, and a vapour absorption system (VAB) for cooling. The overall network, energy efficiency, and exergy efficiency of the IMP were estimated at 183 MW, 61.50% and 44.22%, respectively. The specific emissions were estimated at 122.2, 0.222, and 3.0 × 10⁻⁷ kg/MWh for CO₂, NOx, and CO, respectively. Similarly, the harmful fuel emission factor, and newly introduced sustainability indicators—exergo-thermal index (ETI) and exergetic utility exponent (EUE)—were obtained as 0.00067, 0.675, and 0.734, respectively. The LCC of $1.58 million was obtained, with a payback of 4 years, while the unit cost of energy was estimated at 0.0166 $/kWh. The exergoeconomic factor and the relative cost difference of the IMP were obtained as 50.37% and 162.38%, respectively. The optimum operating parameters obtained by a genetic algorithm gave the plant’s total cost rate of 125.83 $/hr and exergy efficiency of 39.50%. The proposed system had the potential to drive the current energy transition crisis caused by the COVID-19 pandemic shock in the energy sector. Full article

Rapid urbanization, global warming and enhanced quality of life have significantly increased the demand of indoor thermal comfort and air conditioning systems are not a luxury anymore, but a necessity. In order to fulfil this need, it is imperative to develop affordable and environmentally friendly cooling solutions for buildings. In this work, the 3E performance (energetic, economic and environmental) of electrically driven water-cooled vapour compression systems and thermally (solar) driven vapour absorption cooling systems are evaluated and the parameters affecting the performance of solar-driven vapour absorption systems are investigated. The energy simulation software TRNSYS is used to simulate the performance of both systems in order to fulfil the cooling needs of an industrial manufacturing building for the typical climate conditions for Lahore, Pakistan. Primary energy saving, initial investment, operational cost, and carbon footprint indices are used to analyse the performance of both systems. In addition, a parametric code is written in Python and linked with TRNSYS to perform a parametric study to investigate the effects of various parameters such as solar field size, storage tank volume, optimum annual and monthly collector angles, and flow rate in the solar field on the solar-driven vapour absorption chiller performance. The results reveal that around 5% more energy can be absorbed per collector surface area by changing the solar tilt angle on a monthly basis compared to one fixed angle. The analysis shows that electrically driven vapour compression-based cooling systems have much higher running cost and are potentially hazardous for the environment but have lower capital costs. On the other hand, solar thermal systems have lower running costs and emissions but require further reductions in the capital costs or government subsidies to make them viable. Full article

Injection-grout density is an important parameter when its additional weight leads to consolidated decorative plasters becoming damaged. This is especially evident in larger detached areas. In this study, thin-walled soda–lime–borosilicate glass microspheres were used as a density-reducing constituent in hydrated lime grout mixtures. The normal density grout composition—one volume part hydrated lime and three volume parts inert limestone filler with 0.5% of the polycarboxylate ether-based superplasticiser—was modified with partial substitution of the limestone filler with lightweight glass microspheres. The following volumetric proportions between limestone filler and glass microspheres were used: 100%:0%, 67%:33%, 50%:50%, 33%:67%, and 0%:100%. With the increase of the glass microspheres’ volume, the density of the grout is gradually reduced. Furthermore, there is a decrease in the stability and injectability of fresh grout. In its hardened state, the grout’s strength again reduces gradually, but there is no significant change in the grout’s water absorption and water-vapour resistance. The resistance of the grout to freezing–thawing and heating–cooling cycles using distilled water or salt solution is highly improved when the microspheres are present. Full article

In this paper, a heat driven cooling system that essentially integrated an organic Rankine cycle power plant with a vapour compression cycle refrigerator was investigated, aiming to provide an alternative to absorption refrigeration systems. The organic Rankine cycle (ORC) subsystem recovered energy from the exhaust gases of internal combustion engines to produce mechanical power. Through a transmission unit, the produced mechanical power was directly used to drive the compressor of the vapour compression cycle system to produce a refrigeration effect. Unlike the bulky vapour absorption cooling system, both the ORC power plant and vapour compression refrigerator could be scaled down to a few kilowatts, opening the possibility for developing a small-scale waste heat-driven cooling system that can be widely applied for waste heat recovery from large internal combustion engines of refrigerated ships, lorries, and trains. In this paper, a model was firstly established to simulate the proposed concept, on the basis of which it was optimized to identify the optimum operation condition. The results showed that the proposed concept is very promising for the development of heat-driven cooling systems for recovering waste heat from internal combustion engines’ exhaust gas. Full article

Trigeneration plants can use different types of chillers in the same plant, typically single effect and double effect absorption chillers, vapour compression chillers and also cooling storage systems. The highly variable cooling demand of the buildings connected to a district heating and cooling (DHC) network has to be distributed among these chillers to achieve lower operating costs and higher energy efficiencies. This problem is difficult to solve due to the different partial load behaviour of each chiller and the different chiller combinations that can cover a certain cooling demand using an appropriate sizing of the cooling storage. The objective of this paper is to optimize the daily plant operation of an existing trigeneration plant based on cogeneration engines and to study the optimal cooling load sharing between different types of absorption chillers using a mixed integer linear programming (MILP) model. Real data from a trigeneration plant connected to a DHC close to Barcelona (Spain) is used for the development of this model. The cooling load distribution among the different units is heavily influenced by the price of the electricity sold to the grid which rules the duration of the operation time of the engines. The main parameter to compare load distribution configurations is the primary energy saving indicator. Cooling load distribution among the different chillers changes also with the load of the whole plant because the chiller performance changes with load. Full article

Naval surface ships should use thermally driven heating and cooling technologies to continue the Navy’s leadership role in protecting the marine environment. Steam ejector refrigeration (SER) or steam ejector heat pump (SEHP) systems are thermally driven heating and cooling technologies and seem to be a promising technology to reduce emissions for heating and cooling on board naval surface ships. In this study, design and thermodynamic analysis of a seawater cooled SER and SEHP as an HVAC system for a naval surface ship application are presented and compared with those of a current typical naval ship system case, an H₂O-LiBr absorption heat pump and a vapour-compression heat pump. The off-design study estimated the coefficient of performances (COPs) were 0.29–0.11 for the cooling mode and 1.29–1.11 for the heating mode, depending on the pressure of the exhaust gas boiler at off-design conditions. In the system operating at the exhaust gas boiler pressure of 0.2 MPa, the optimum area ratio obtained was 23.30. Full article

We report on the development of a photoacoustic sensor for the detection of formaldehyde (CH₂O) using a thermoelectrically cooled distributed-feedback quantum cascade laser operating in pulsed mode at 5.6 mm. A resonant photoacoustic cell, equipped with four electret microphones, is excited in its first longitudinal mode at 1,380 Hz. The absorption line at 1,778.9 cm^-1 is selected for CH₂O detection. A detection limit of 150 parts per billion in volume in nitrogen is achieved using a 10 seconds time constant and 4 mW laser power. Measurements in ambient air will require water vapour filters. Full article