The liquid film desiccant cooling system is gaining increasing attention because of its superiorities over the conventional vapor compression cooling system. In this paper, a 3D falling film dehumidification model on a pillow plate was established. The effects of the pillow plate's geometric parameters, such as pitch ratio, maximum inner channel height, and weld-spot diameter, on dehumidification performance were analysed in relation to liquid film thickness, flow velocity distribution, vortex formation, and both moisture removal and dehumidification efficiency. The results indicate that the weld-spots of the pillow plate induce apparent secondary flows that enhance heat and mass transfer performance. The effects of geometric parameters on the falling film dehumidification performance are not monotonous, with the highest dehumidification performance is achieved when the geometric parameters of the pillow plate are pitch ratio of 1.89, maximum inner channel height of 9.0 mm, and weld-spot diameter of 10.0 mm. Compared to a flat plate, the pillow plate primarily enhances mass transfer by changing the activity of the vortex from deformation motion dominated to rotation motion dominated near the gas-liquid phase interface. Furthermore, under the same operating conditions, the pillow plate produces an absolute moisture removal and dehumidification effectiveness increase 55.88 % and 55.89 %, respectively, comparing with the flat plate.

Ionic liquids (ILs) offer significant advantages as alternative absorbents in absorption refrigeration cycles due to their superior physicochemical properties. Assessing the performance of new IL-based working pairs in absorption systems is essential for their rapid application in industrial applications. This study evaluates the water absorption performance of an aqueous solution of 1-ethyl-3-methylimidazolium acetate ([EMIM]Ac) under both saturated atmospheric and vacuum conditions. Additionally, the performance of an absorption chiller utilizing the [EMIM]Ac/H2O 2 O working pair was analysed using the Aspen Plus process simulator. A discrepancy was observed between the water vapor pressure in the air and the saturated vapor pressure of the aqueous solution at equilibrium. A theoretical criterion for the minimum relative humidity required for effective water vapor absorption by this absorbent at a given mass fraction is proposed. Under vacuum conditions, lower absolute pressure or higher mass fraction enhances absorption. Surfactants significantly improve absorption performance, with 2-octanol and 1-octanol demonstrating approximately double the absorption capacity compared to [EMIM] Ac. Higher mass fractions of the aqueous solution enhance the absorption rate but reduce the desorption rate. The coefficient of performance (COP) COP ) of the system decreases with increasing pressure and mass fraction, reaching a peak of 0.9 at a mass fraction of 20 % and a pressure of 3 kPa. Lower pressure and mass fraction enhance exergy efficiency.

Enhanced heat and mass transfer in a falling film liquid desiccant dehumidifier is crucial for improving the efficiency of liquid desiccant air conditioning systems. However, no study has yet been undertaken to examine the impact of a range of different enhancing elements on dehumidification performance. This study comprehensively investigates and compares falling film hydrodynamics and dehumidification performance on plates with various enhancing elements based on different air inlet velocity and humidity, solution inlet velocity, and concentration, as well as enhancing element spacing and height. The results demonstrate that, under a variety of working conditions, the dehumidification performance of the plate with isosceles right triangle shaped finned elements (plate No. 3) is superior to that of other plates. The dehumidification performance of plates with finned elements is superior to that of plates with grooved elements under the same condition. For plates with isosceles right triangle shaped finned elements, the impact of the flow field caused by the elements is greater than in other shapes due to the greater intensity of the gas-liquid perturbation and mixing, resulting in an enhanced dehumidification performance. The findings of this study may prove valuable in the optimization of dehumidifier structures in the context of liquid desiccant dehumidification performance enhancement.

Falling film evaporators are commonly employed in a wide range of industrial applications, with a particular emphasis on the management of vapor generated during operations. It is widely recognized that vapor streams have a significant influence on falling film flow and heat transfer. In this paper, we conducted numerical investigations of this issue in the presence of vertical vapor streams and validated the present numerical results against previous experimental data. The results indicate that the length of the liquid tongues and the interaction time between two liquid films are affected by both downward and upward vapor streams. The effect of vertical vapor on the film thickness is dependent on the vapor's orientation and position on the tube. Typically, is decreased by 25 % at z* = 0 and vg = 4.0 ms-1 and is increased by 20 % at z* = 0 and vg = 4.0 ms-1. The downward vapor enhances heat transfer on the top half of the tube's periphery while weakening it on the bottom half, while the upward vapor contributes to heat transfer enhancement mainly in the detachment zone. Overall, the vertical vapor stream causes substantial redistributions of the heat transfer coefficient, velocity vector, and liquid film thickness in three distinct zones. Downward and upward vapor streams predominantly impact the upper and lower parts of the tube, respectively. Within the current velocity range, it is evident that vertical vapor streams consistently lead to an average enhancement in heat transfer.

The floor radiant heating system is widely used in various buildings due to its advantages such as high efficiency, comfort, and uniform heating. Generally, research on floor radiant heating systems focuses on energy saving, but the issue of slow thermal response during the heating process has not been solved. To solve the problem of slow thermal response and uneven indoor thermal environment in floor radiant heating systems, a fuzzy logic control theory based on optimal fuzzy rules was proposed. The floor radiant heating system based on fuzzy logic control was established by the TRNSYS-MATLAB integrated control platform. The study compared the thermal response and thermal comfort performance of PID control, fuzzy logic control, and optimized fuzzy control methods. The results showed that fuzzy logic control performed better than PID control in controlling the system's thermal performance and indoor thermal environment. Compared to PID control, the optimized fuzzy control reduced the thermal response time by 64.60%, and the total energy consumption of the water pump and heat pump decreased by 222 kWh and 329 kWh, respectively. The proposed fuzzy logic control demonstrates favorable thermal response characteristics and holds substantial potential for energy conservation within the increasingly prevalent floor radiant heating systems.

Porous surfaces often exhibit exceptional performance in liquid spreading and heat transfer, making them promising candidates for enhancing falling film heat transfer on solid surfaces. This paper delves into the flow and heat transfer characteristics occurring within falling films on horizontal tubes coated with a porous layer. To achieve this, a three-dimensional numerical model that couples the Volume of Fluid (VOF) method with porous media considerations was employed. The investigation comprehensively covers film spreading behavior, flow patterns, film velocity, film thickness, temperature distribution, and heat transfer coefficients, for both plain and porous tubes. Furthermore, we delve into the effects of key parameters, such as porosity, layer thickness, and material properties, on the overall heat transfer process. The results demonstrate the accuracy of our model in reproducing film thickness and heat transfer coefficients within falling films on horizontal porous tubes. When comparing plain tubes to porous ones, some key differences emerge. Specifically, the liquid film on porous tubes spreads more slowly, leading to increased film thickness and fewer occurrences of dry patches. Additionally, porous tubes result in lower film velocity and a more uniform temperature field compared to plain tubes. Interestingly, the findings reveal that smaller porosities yield thicker films and higher heat transfer coefficients, particularly when the porosity is below 0.4. Moreover, thicker porous layers result in thinner films, higher wetting ratios, and increased heat transfer coefficients. Among the materials we tested, aluminum and copper porous layers exhibit the highest heat transfer performance, while steel demonstrates the lowest.

Agricultural greenhouses play a crucial role in addressing the threat of climate change to agricultural systems. The greenhouse systems control exhibits nonlinear characteristics and large lag, both affecting the regulation of the greenhouse thermal environment. In this paper, a control strategy was designed to set the dynamic reference value of the control objective of the greenhouse model, considering factors such as solar radiation and the heating capacity of water body. A complete greenhouse model was developed using TRNSYS, and then the model predictive control building and optimization were implemented through MATLAB. The control effects of traditional proportional-integral-differentiation control, initial model predictive control, and optimized model predictive control were compared. The results showed that the regulation of greenhouse temperature was improved by 10.6% in the coldest mouth compared to the conventional proportional-integral-differentiation control by the optimized model predictive control. During a typical cold month, the violation of constraints was reduced by 29.7% by dynamically setting the target of the greenhouse with the optimized model predictive control. The performance of greenhouse climate control is enhanced by the proposed optimized model predictive control method, ensuring a stable regulation of the crop growth environment.

Falling film flow and heat transfer are extensively encountered in various industries of renewable and sustainable energy due to the outstanding heat transfer performance. The predictions in falling film hydrodynamics and heat transfer are crucial for the optimal design of falling film heat exchangers, and there have been considerable advancements made in this area over the past few decades. Considering the gaps in current literature predictions, this paper aims to present a comprehensive review on the correlations of flow pattern transition, film thickness, heat transfer, and liquid film rupture within falling film flowing over horizontal tubes and tube bundles. Through comparisons and summarizations, it can be found that the documented correlations appear to be significantly out of alignment with one another, which greatly restricts the applicability of these predictions. The correlations of falling film thickness that are obtained using regression approach based on dimensional analysis may take into account more factors than the ones modified from Nusselt theory. The predictions of flow pattern transition of falling liquid film with horizontal column are often described as the functions of the film Reynolds number, derived from the Kapitza number or the Galileo number. The functions of Nusselt number, film Reynolds number, Prandtl number, and Archimedes number are typically used to represent sensible and evaporative heat transfer correlations, whereas boiling heat transfer correlations also take into account the influence of heat flux, such as Boiling number. The full process of actual heat transfer is taken into account from both the standpoints of sensible convection and nucleate boiling using the combination functions of various heat transfer forms. Within the ranges of their own parameters, the well-established heat transfer models often offer good accuracy. While the predictions of phase change heat transfer often behave worse, the predictions of sensible heat transfer are more general and accurate. Generally speaking, the minimum film flow rate or the maximum heat flux were the functions that correlated with the inceptions of liquid film rupture.

Vapor shearing is a common issue encountered in the operations of falling film heat exchangers. The vapor stream effect depends on its orientation. This study investigates liquid film hydrodynamics and heat transfer performance under the influence of vapor streams from different orientations. The results indicate that both orientation and velocity of vapor determine the encountering time and position of the films on the tube's two sides. The liquid film thickness uniformity and the liquid column deflection vary significantly depending on the orientation and velocity of the vapor. Zones of accelerated liquid film, climbing liquid film, liquid stagnation, and transition of liquid film flow pattern are observed. The gradient of film thickness along the tube axis and the deflection in time-averaged peripheral film thickness increase as the vapor orientation varies from 0° to 90° and subsequently decrease as the vapor orientation varies from 90° to 180°. Vapor streams have more pronounced effects on time-averaged peripheral film thickness in regions close to the liquid inlet and outlet. Vapor streams result in changes in peripheral heat transfer coefficients toward the downstream side depending on the orientation and velocity of the vapor. The impact of vapor streams on the overall heat transfer coefficient does not directly correlate with the velocity of the vapor when maintaining the same orientation.

Secondary flows induced in helical-coiled pipes significantly enhance the thermal storage performance of latent heat thermal energy storage units. This paper presents a three-dimensional model of a triple-pipe helical-coiled system to investigate the melting characteristics of phase change material within it. A correlation for the complete melting time was developed based on the simulation results. The findings indicate that the thermal- hydraulic fields of the heat transfer fluids and phase change material deflect from the vertical central axis at cross-sections. The secondary flows within the inner pipe are more effective in enhancing melting than those in the outer pipe. Melting performance improves with increasing inner pipe diameter, coil diameter (from 100 mm to 160 mm), inclination angle, or heat transfer fluid temperature, or decreasing helical pitch. The inner pipe diameter, helical pitch and heat transfer fluid temperature exhibit more pronounced influences. An inner pipe diameter of 30 mm, a coil diameter of 160 mm, a helical pitch of 80 mm, an inclination angle of 90 degrees, a heat transfer fluid temperature of 360 K, and a heat transfer fluid Reynolds number of 2000, respectively produce a faster melting process. The developed correlation for the triple-pipe helical-coiled pipe thermal storage unit accurately predicts 96 % of the 45 data within +/- 11 %.

Due to a number of benefits, liquid desiccant dehumidification has received a lot of attention lately. In comparison to previous improvement strategies, corrugated plates have demonstrated higher efficacy in liquid desiccant dehumidification. This study employs computational fluid dynamics to examine the dehumidification performance of falling film liquid desiccant dehumidification on over sinusoidally shaped corrugated plates. The effects of plate geometries, solution parameters, and moist air (concentration of humidity, temperature, and flow rate) were discussed. Additionally, a mass transfer correlation was proposed based on the current numerical data. It is indicated that the corrugated plate significantly enhances dehumidification performance due to the liquid film waves intensification, mass transfer area expansion, and induction of vortexes close to the gas-liquid interface. The most effective falling film dehumidification is achieved using a corrugated plate with a wavelength of 5.0 mm and an amplitude of 0.5 mm. By raising the solution or air inlet temperature, the dehumidification rate is reduced while being strengthened by raising the solution or air inlet concentration, velocity, or air humidity. While decreasing when solution intake concentration or air velocity rises, the efficacy of dehumidification rises as solution velocity does. The proposed mass transfer correlation accurately predicts 93.3 % of the 45 data, with an error of 11 % or less. In the current parameter scopes, the magnitude has a more significant effect on Shair than the wavelength. Adjustments to air velocity and solution concentration can cause significant fluctuations in Shair, while air and solution temperature have little effect on Shair.

The dynamic behaviour and performance evaluation of a biomass-fired organic Rankine cycle combined heat and power (ORC-CHP) system under two different control strategies are investigated in this study. The dynamic model is established, while the dynamic characteristics of key operating parameters (superheat degree, evaporating pressure and mass flow rate) with the step change of heat source temperature are examined. The effects of controlled superheat degree and controlled expander shaft work on dynamic behaviours of thermodynamic, economic and environmental performance are discussed and compared under different control methods (feedforward active control, PID passive control and combined control). Results indicate that the superheat degree is significantly influenced by the heat source temperature under the without control strategy, with the variation reaching 8.4 K. The combined control method exhibits the best control performance with overshoot and control response times of 1.2 K and 12.3 s, respectively. Compared to without control, the expander shaft work and ORC thermal efficiency of the control strategy of superheat degree increase by 3.2 kW and 0.8 %, while that of the control strategy of expander shaft work increase by 1.0 kW and 0.3 %, respectively. The control strategy of superheat degree presents a significant improvement in the economic and environmental performance of the biomass-fired ORC-CHP system. This study is expected to provide better guidance for the practical operation and control of biomass-fired ORC-CHP systems.

The impact and rebound dynamics of droplets on superhydrophobic surfaces were investigated through numerical analysis employing the phase field method. The influences of contact angle, impact velocity, surface tension, and dynamic viscosity on the fields of pressure and velocity as well as the spreading factor and central height were described comprehensively. The results indicate that there are a series of stages of impingement, spreading, transition, retraction, and rebound in order throughout the life cycle of a droplet. The droplet exhibits distinct pressure and velocity profiles upon impingement stage, with the maximum pressure at the lower center and higher velocities at the upper periphery, spreading around. Velocities are predominantly upward, peaking at the bottom of the droplet during the rebound stage. A larger contact angle, viscosity, surface tension, and lower impact velocity contribute to a reduced maximum spreading factor. Deposition is more likely to occur when the impact velocity, surface tension is lower, and the viscosity is larger. Droplets tend to rebound when the contact angle, impact velocity, and surface tension are larger. Thresholds for impact velocity, surface tension, and viscosity were delineated for droplet rebound. Furthermore, a correlation for predicting the maximum spreading factor of droplets on superhydrophobic surfaces was proposed.

In this paper, single-phase heat transfer characteristics of water inside internal enhanced tubes were investigated. Refrigerants are boiling or condensing outside the tube. The experimental tubes have internal helical rib heights of 0.25-0.36 mm, helix angles of 40-60 degrees, rib base thicknesses of 0.40-0.79 mm, rib tip thicknesses of 0.078-0.283 mm, and Ns (starts number per circle) of 40-50. It shows that the heat transfer enhanced ratios usually range from 2.3 to 3.64. The friction factors relative to the smooth tube are about 1.8 to 3.3 times higher. Analyzing the effect of rib geometry on flow and heat transfer, it was found that the higher the height of the internal rib, the better the enhancement of convective heat transfer in the tube. Also, the greater the thickness of the rib tip and base, the more detrimental to the friction factor in the tube. There was no noticeable influence on the heat transfer performance as the helix angle increased from 45 degrees to 50 degrees. For the increase of Ns, it appears that 45 ribs per circle is the best value in the present study when considering the increase in pressure loss. The thermal-hydraulic performance of 11 tubes was also evaluated. It shows that Tube-1 had the best performance in the condensing tubes and Tube-7 had the best performance in the boiling tubes.

This article focuses on evaporative falling film heat transfer through numerical simulations. A two-dimensional symmetric liquid film flowing outside a single horizontal tube was simulated using the open-source CFD software OpenFOAM. The Tanasawa model was employed to consider mass transfer at the liquid-vapour interface, and the isoAdvector VOF method was used for interface tracking. The simulations explored the impact of film flow rate, tube surface heat flux, and tube diameter on the liquid film thickness and surface heat transfer coefficient. Additionally, the critical heat flux and operational limits were considered. The results demonstrate the accurate reproduction of evaporative falling film heat transfer performance by the present model. The film thickness exhibits a similar profile to adiabatic and sensible falling film heat transfer but provides smaller values. Similarly, the evaporative heat transfer coefficient exhibits significantly higher values and a gentle peripheral variation. The influence of heat flux on evaporative falling film heat transfer is contingent on the film flow rate; it can either enhance or weaken the process. Notably, a larger tube diameter negatively affects heat transfer, suppressing the impact of heat flux, and also increases the risk of liquid film dryout. For a given film flow rate, the average heat transfer coefficient increases initially, reaches a maximum value, and then decreases as the wall heat flux is increased. The peak heat flux, termed critical heat flux, increases with film flow rate but decreases with tube diameter. An operational limit exists where the heat flux is lower than the critical heat flux and the film flow rate is higher than the critical film flow rate; under these conditions, evaporative falling film heat transfer operates in a fully wetting status.

Greenhouses rely on an appropriate environment to support vegetable growth, and multi-pipe earth-to-air heat exchangers (EAHEs) are commonly used to regulate the temperature. In greenhouses, the high humidity resulting from plant respiration and transpiration has a significant effect on the thermal performance of EAHEs. This study employs the Taguchi method to optimize the multi-pipe EAHE for greenhouse applications, and high humidity conditions were taken into account. A complete greenhouse model was established, and experiments were conducted in Shandong province with real-time monitoring data used to verify the thermal environment of the greenhouse. Multivariate analysis was performed on EAHE parameters to evaluate their integrated performance. The optimized design combination was then implemented in the greenhouse. The findings reveal that the inlet air temperature exerted the most substantial influence on the integrated performance of the EAHE system, contributing significantly with a percentage of 45.20%. The velocity of the inlet air and diameter of pipes followed with contributions of 21.98% and 18.39%, respectively. The optimized EAHE system significantly improved the greenhouse's thermal environment, with the air diffusion performance index (ADPI) increasing to 65% and 98.33% at noon and midnight, respectively, making it more suitable for tomato growth. This study provides guidelines for selecting EAHE parameters in greenhouse applications, paving the way for the widespread use of EAHE systems in greenhouses.

Boiling heat transfer is widely used in industry and daily life and can be enhanced by porous media structure. Previously HPM have been shown to significantly improve heat transfer performance, but how the porosity gradient affects boiling heat transfer remains unknown. In this paper, the subcooled flow boiling in vertical square channels partially filled with gradient porous media was numerically investigated by using a newly developed solver named GPMPhaseChangeFoam embedded in the open-source platform OpenFOAM. The results indicate that in positive GPM inserted channels, when z <= 0.16 m Nu(z) increases with increasing H-p*, and when z >= 0.16 m Nu(z) increases with increasing H-p* from 0.2 to 0.8 but deceases with H-p* rises from 0.8 to 1.0, and the effect of H-p* on Nu(z) is more pronounced in the entrance region over the exit region. In negative GPM inserted channels, Nu(z) increases with increasing H-p* throughout the channel length in positive GPM inserted channels, and the effect of H-p* on Nu(z) is less pronounced in the entrance region than the exit region. Flow resistance increases with H-p*, but changes little with Delta epsilon, and Nu(fd) increases with H-p* in both positive and negative GPM inserted channels. However, Nu(fd) decreases with an increase in triangle epsilon from 0 to 0.3 in positive GPM inserted channels, from -0.3 to 0 in negative GPM inserted channels, and triangle epsilon = -0.3 at H-p* = 1.0 is 13.4 % higher than that of triangle epsilon = 0.3. Furthermore, the negative GPM inserted channel behaves higher flow boiling heat transfer performance than the HPM and positive GPM.

Sustainable development objectives place a high priority on entrepreneurship and renewable energy. Supporting entrepreneurial activities in the renewable energy industry can provide economic growth and employment to accomplish the Sustainable Development Goals Agenda 2030. Solar water heating systems can provide clear benefits for both the environment and economic growth. There is a gap in the literature regarding the study of the factors hindering or driving the development of the solar water heating system industry. This study aims to investigate the solar water heating system industry’s challenges and attempts to define the drivers to further develop the industry. Thus, solar water heating entrepreneurship parameters can be identified. Additionally, energy savings and carbon dioxide emissions were calculated for the region to raise awareness among consumers. This study used the qualitative analysis method through semi-structured interviews with 40 business owners in Adana/Turkey. The findings showed that the industry has administrative, production, political, and economic issues; there is a need for economic support and expanding education and control mechanisms. Also, the payback period is 1.63~3.27 years for a solar water heating system and this system prevents 800.75 kg of CO2 emission. The study has implications for policy-making, practice, scientific research, and the SDGs Agenda 2030.

Numerical method is used to investigate fully developed laminar flow in helically coiled circular tube in this paper. The non-dimensional parameter (secondary flow Reynolds number Se) based on absolute vorticity flux along the mainstream is used to indicate the intensity of secondary flow caused by the centrifugal effect in helically coiled circular tube. The relationship between the intensity of secondary flow and the intensity of laminar convective heat transfer is studied. The effects of curvature and torsion on the enhancement of heat transfer are also considered. The results reveal that the absolute vorticity flux along the mainstream can be used to indicate the local or averaged intensity of secondary flow; the non-dimensional parameter of the absolute vortex along the main flow determines the convective heat transfer and friction factor. The relationships of Nusselt number and friction factor with the Se are obtained. The effect of curvature on Nusselt number is obvious, but the effect of torsion on Nusselt number is less obvious.