Outlet Air Temperature Research Articles

Experimental Investigation for the Performance of the Solar Air Dryer with Vortex Generator

Experimental simulations were conducted to analyze the thermal properties of a solar air dryer embedded with a delta-winglet vortex generator (DWVG). The present inquiry goal is to enhance the thermal performance of the solar air dryer. The delta-winglets were placed at the bottom absorber duct surface. Eight pairs of DWVG were considered for relative height (e/H) ratio from 0.2 to 0.6, an angle of attack (ß) was preserved at 60°, and the pitch-ratio (p/e) was equal to 10. This experimental investigation was performed for 0.022kg/s (MFR) and solar irradiance varied from (300 to 920) W/m2. The winglet vortex generators were set in a common flow-down configuration. The impact of (DWVG) on thermal efficiency and useful thermal energy was discussed. The thermal efficiency (η) and useful thermal energy (Qu) at 0.6 (e/H) appear improved up to about 6.5% and 9.4% respectively, higher than a smooth solar air dryer. The (DWVG) affects outlet air temperature, resulting in a considerable increase in the heat transfer convective rate.

Experimental studies on drying characteristics of green chilies in a solar dryer

Green and clean technology is the demand of today’s world. Solar dryer, for drying agriculture produce is one of the major applications of the solar energy. The flat plate air collector plays crucial role for drying the agricultural produce in solar dryer application. This research work, focuses on the design and development a solar collector for drying agriculture produces using waste aluminum cans of beverages. A solar air collector is designed and developed in the laboratory as per IS 1933, 2003 standard. A solar collector developed has been tested and an overall performance of the system is evaluated for three different mass flow rates (0.01 kg/s, 0.008 kg/s and 0.006 kg/s) for drying 15 kg of green chilies. The selective coating material made by mixing activated charcoal and black board paint is applied on the cylindrical curved surface of the tubes considering the critical radius of insulation. The inlet and outlet temperature of air has been recorded for different mass flow rate and the overall collector efficiency is calculated. Further, the moisture removal rate from green chilies is evaluated for every 30 minutes of time interval in a day. It is found that the efficiency is decrease with increase in mass flow rate. A maximum moisture removal rate of 88% is observed for a mass flow rate of 0.01 kg/s and the maximum efficiency of solar collector of 50.27%. is attained for a mass flow rate of 0.006 kg/s.

Performance analysis of induced draft cooling tower integrated with rotary silica gel mesh

AbstractA humid environment decreases the performance of induced draft counter flow cooling towers (IDCFCT) normally used in power plants and process industries. The primary objective of this study is to experimentally analyze the effect of using rotary silica gel mesh (RSGM) on the performance of IDCFCT. Experimental setups of IDCFCT with and without RSGM have been designed and fabricated to perform the comparative analysis. The performance of both cooling towers (CTs) in terms of output temperature, relative humidity of air, range, approach, and effectiveness at different air velocities has been investigated. The results indicate that the outlet air temperature of IDCFCT integrated with the RSGM wheel is 0.5–1.5°C higher than the IDCFCT without the RSGM wheel. IDCFCT with RSGM wheel shows maximum effectiveness of 0.67 at an air velocity of 1.5 m/s and inlet water temperature of 55°C; whereas, for IDCFCT without RSGM wheel, it is only 0.54. In terms of efficiency, RSGM wheel integrated IDCFCT shows an improvement of 24% compared to IDCFCT without RSGM wheel. It has been observed that RSGM‐integrated IDCFCT also helps to save water up to 431.7 kg/h at an air velocity of 1 m/s with a water inlet temperature of 35°C. Moreover, the advantage of integrating the RSGM wheel with IDCFCT has been further corroborated in terms of the reduction in the height of the CT obtained with the help of a thermodynamic model.

Experimental study on the heating performance of transcritical CO2 heat pump for electric buses

In this paper, a transcritical heat pump using CO2 as the refrigerant was developed, and the heating performance test experiment was carried out in the standard bus air conditioning performance enthalpy difference laboratory to explore the influence of outdoor temperature, compressor speed and electronic expansion valve (EEV) opening on the performance of the heat pump system. Operating at −25 °C/20 °C (outdoor temperature is −25 °C, indoor temperature is 20 °C), the heating capacity (Q) of the CO2 heat pump is 10.5 kW, the coefficient of performance (COP) is 1.24, indicating that the system can also effectively save energy under ultra-low temperature conditions. As the compressor speed rises, the COP of system drops sharply, so the compressor operating frequency should be reduced as much as possible under the premise of satisfying the Q and outlet air temperature (Ta.out). Increasing the opening of the EEV can effectively reduce the compressor exhaust temperature (Tcom.out) and pressure(Pcom.out) to ensure the safe and stable operation of the system.

CFD analysis of the earth air pipe heat exchanger with helical geometry for optimum space utilisation

ABSTRACT The helical geometry of the air pipe is used in present study, under transient conditions to improve the cooling effect and performance of the Earth Air Pipe Heat Exchanger (EAPHE). The helical layout design of the air pipe decreases the area required for installation by up to 70%. The performance of the EAPHE system deteriorates because of the thermal saturation of nearby sub-soil. Aluminium water pipe is installed at the centre of the helical pipe for the thermal saturation of sub-soil. Heat is absorbed by the nearby soil through a water tube that acts as a thermal reservoir as water has the highest specific heat. FLUENT 19.0 is used for the development and simulation of the CFD model. The results show that after 24 h the system maintains a constant heat transfer rate and gives constant air outlet temperature.

Numerical analysis of heat transfer characteristics of a novel heat exchanger for Lorenz-Meutzner cycle with zeotropic mixtures

This study evaluates the performance enhancement of the Lorenz–Meutzner (LM) cycle with zeotropic mixtures of multiple refrigerants using a numerical simulation model. The computational simulation includes a heat exchanger model developed for predicting the air outlet temperature accurately. The predicted results are validated against experimental gliding temperature with varying mass fractions of different zeotropic mixture combinations. The R600/R290 mixture demonstrates the best performance characteristics. Various design changes of the heat exchanger are adopted to enhance the energy efficiency of the LM cycle. Counterflow configuration is found to be superior to the parallel configuration, particularly in the LM cycle, owing to the gliding temperature difference of zeotropic mixtures. Multiple refrigerant flow paths decrease the air outlet temperature further and prove to be more effective than the single flow path design. Based on careful investigation of the geometrical effect of heat exchangers on the LM cycle, a novel design of the heat exchanger is proposed, and its overall performance in the LM cycle is evaluated. The novel design of the heat exchanger indicates the largest air temperature difference, leading to the highest coefficient of performance (system energy efficiency) of the LM cycle compared with the baseline cycle with R600a.

Numerical Investigation of Air Entrainment and Outlet Temperature Characteristics of a Convex-Type Infrared Suppression Device

AbstractInfrared suppression devices (IRS) are frequently used in naval/cargo ships to passively entrain an additional amount of cold air from the atmosphere, and mix it with the hot plume so as to suppress its temperature, and the IR signature. In this work, a convex-type IRS device has been proposed consisting of five numbers of the convex-type funnels. The air entrainment ratio has been numerically computed by solving the transport equations (i.e., mass, momentum, energy, turbulent kinetic energy, and its dissipation rate in a structured grid arrangement by employing a pressure-based finite volume solver in ansysfluent. The pertinent parameters like the Reynolds number, inlet temperature ratio, convex-radius ratio, and funnel-overlap height have been varied in the range of −1.5 × 105 to 1.5 × 106, 1.243 to 2.576, 0.834 to 1, and 0 to 0.326, respectively. It has been observed that the air entrainment ratio increases with both the Reynolds number and convex-radius ratio for the considered temperature ratios. An optimum convex-radius ratio (=0.909) has been obtained, where the air entrainment and the outlet temperature become the maximum and the minimum, respectively. Both the inlet temperature ratio and overlap height significantly improve intake of cold air into the IRS device due to the additional buoyancy force, and the enhanced area availability for air the ingestion. The convex-type IRS device performs better than a cylindrical-type IRS device. A nonlinear regression model based on the Levenberg-Marquardt (L-M) method has been deployed to develop a correlation equation for the air entrainment.

Influencia de la composición del alimento y el proceso de secado por aspersión en la calidad de una mezcla de mora en polvo (Rubus glaucous Benth)

The Castile blackberry (Rubus glaucus Benth) is a fruit rich in active components, which is framed within the context of functional foods, to provide well-being to the human being. The objective of the research was to evaluate the effect of the feed composition and the spray drying process (SD) on the quality of the blackberry powdered mixture (BPM). The response surface methodology was used with a central composite face-centered design (α=1), considering the following independent variables: inlet air temperature (IAT) (140 - 160 °C), outlet air temperature (OAT) (80 - 90 °C), atomizer disk speed (ADS) (20000 - 24000 rpm) and maltodextrin (MD) (5 – 9 %). The dependent variables were water activity (aw), humidity (Xw), solubility (S), wettability (We), hygroscopicity (H), angle of repose (AR), particle size (Span), total phenols (TP), antioxidant activity (ABTS and DPPH), anthocyanins (A), ellagic acid (EA) and product yield (Y). In general, We is the most critical variable in BPM, being statistically affected by most of the independent variables and by their linear and quadratic interactions. On the other hand, the experimental optimization of multiple responses defined the independent variables as IAT (159.3 °C), OAT (89.3 °C), ADS (24000 rpm), MD (5.5  %), and the dependent variables as aw (0.166±0.002), Xw (7.10±0.05 %), S (88.01±0.17 %), We (54.4±1.3 min), AR (7.4±3.7°), Span (1.69±1.04), TP (4513.1±23.5 mg AGE/100g dry base (db), ABTS (4012.7±34.0 mg TE/100g db), DPPH (5359.4±39.1 mg TE/100g db), A (281.2±29.4 mg C3G/100g db), EA (2653.0±155.0 mg/100g db) and Y (46.4±13.2 %). The spray drying (SD) process provides effective protection for the active compounds of the blackberry extract. In addition, it guarantees physicochemical stability for storage.

Evaporative pre-cooling of a condenser airflow: investigation of nozzle cone angle, spray inclination angle and nozzle location

ABSTRACT In hot and dry areas, evaporative cooling can enhance the performance of air-cooled condensers. Pre-cooling of a condenser airflow in a channel by a spray nozzle has been studied numerically. The Eulerian-Lagrangian 3D equations for two-phase flow have been discretized using the finite volume method. An experimental setup has been prepared to validate the numerical model. The effects of nozzle cone angle, spray inclination angle, and nozzle location in the channel have been investigated on the outlet air temperature, droplet evaporation rate, and spray cooling efficiency. The results represent that, between four analyzed geometrical parameters, nozzle longitudinal location is the most important parameter and the spray inclination angle has the lowest degree of importance. Spray inclination angle analysis displays that the counter-flow condition of the nozzle is more efficient than co-flow and cross-flow conditions. The case with the nozzle height of 45 cm in the duct, spray inclination angle of 180 ∘ , and nozzle cone angle of 60 ∘ is the best case. The maximum and minimum spray cooling efficiencies among the cases are about 30.5% and 21%, respectively. Hence, the nozzle geometrical parameters can affect the evaporative cooling capacity up to 45%.

Modeling and assessing earth-air heat exchanger using the parametric performance design method

ABSTRACT Earth-air heat exchanger (EAHE) is a passive technique that can reduce the energy consumption for indoor heating and cooling. This paper aims to evaluate the performance of EAHE in Qingdao, China by using a proposed all-in-one simulation model according to the parametric performance design method. This model can predict the performance and feasibility of EAHE and generate various required results with just one click. It was also validified by the actual field experiment to prove its appropriateness. In the simulation, the influence of eight parameters on the outlet air temperature was firstly analyzed to understand their interrelationships. Secondly, thermal capacity and heat transfer efficiency were evaluated to test the performance of EAHE. Finally, this paper provided a feasibility analysis of EAHE. The findings indicate that deeper burial depth, longer tube length, and smaller tube diameter can achieve better heat transfer efficiency and thermal capacity. However, when tube length exceeded 40 m, burial depth exceeded 2 m, or tube conductivity was higher than 1W/m-K, the change in the outlet air temperature was no longer substantial. More importantly, the feasibility analysis suggested a promising application prospect for EAHE in Qingdao. The maximum average daily cooling and heating capacities of the system were 15.56 kW and 18.49 kW, respectively. The maximum heat transfer efficiency of the system in July (86.02%) and January (87.89%) can be obtained, when the tube length was 70 m and the inlet airflow speed was 1 m/s, respectively. The economic feasibility analysis indicated that EAHE could save 507.8 Yuan each year, and the payback period was about 6.2 years.

Role of Thermal Energy Storage Technology in the Decarbonization of Energy Sector Process – Packed Rock Bed Parameters Analysis

Abstract The paper presents the adiabatic installation of compressed gases energy storage. The authors present the results of analyzes for this type of installation due to the selection of thermal storage material. The simulations were carried out for basalt, granite and ceramics (alumina) as well as for porosity value from 0.375 to 0.39 of basalt-filled reservoirs in Thermal Energy Storage (TES) installation. Characteristics of outlet air temperature, air pressure drop amount of energy stored and external heat losses as a time functions during the charging phase are presented. The research indicated that due to the lowest density and average heat capacity of the materials studied, granite has the fastest and most intense physical exit loss from the storage tank which was approximately 1100 W. However, there was no significant effect on air pressure drop depending on the chosen accumulation materials. The effect of rock bed porosity on the pressure drop of flowing air was investigated. For a constant mass flow rate, pressure drop values ranging from 2200 Pa to 6200 Pa were obtained depending on the porosity value.

Numerical and experimental studies on a pressurized hybrid tubular and cavity solar air receiver using a Scheffler reflector

• Coupled optical and thermal model of a pressurized tubular and cavity solar air receiver. • Modelled the dynamic variation of concentrated solar radiation input to the receiver cavity surface. • Three-dimensional CFD analysis is performed on the hybrid receiver model. • Validation with on-sun experimental results using a Scheffler dish. • Natural convection and radiation heat loss estimation. In this study, a pressurized tubular and cavity solar air receiver is analyzed numerically, and the results are validated experimentally using a Scheffler fixed focus concentrator. Transient numerical analyses for periods similar to experimental testing duration allows realistic performance prediction of new receiver designs and help in understanding the dominant heat loss mechanisms, thus mitigating or reducing them. A coupled optical and thermal model is developed for analyzing the receiver with a novel method of capturing the spatial and temporal variation in the heat input to the receiver. The concentrated heat flux input to the receiver is defined as the product of two separate functions. The first function defines the incident radiation to the receiver as a spatially resolved flux profile on the cavity inside surface, obtained from the ray tracing algorithm. The second function captures the transience in heat input by curve-fitting the measured direct normal irradiation variation with time corresponding to the experimental testing period. Receiver heat loss modelling involves natural convection heat loss from the inside cavity surface estimated using an existing correlation, while radiation heat loss is estimated by prescribing the surface emissivity and computing the ambient view factor. A three-dimensional transient CFD analysis is performed on the hybrid receiver model under identical heating conditions as experiments to predict the flow heat transfer. The result from the numerical model is subsequently compared with on-sun experimental results obtained using a test rig equipped with a Scheffler dish for heat input and supply of compressed air as the heat transfer fluid through the receiver. The deviation between numerical and experimental results are less than 16 °C for air outlet temperature and less than 9% for the receiver thermal efficiency, thus proving the effectiveness of the coupled optical and thermal model. To account for the transient nature of the receiver heating during the on-sun experiments, the receiver thermal efficiency definition has been modified to include the thermal inertia of the receiver material. It is also observed that natural convection is the dominant heat loss mechanism for the present configuration and can significantly reduce the overall thermal efficiency of a receiver. The present numerical model incorporating an optical model of the solar field and as-measured variation of solar radiation input can be effectively used for optimizing the design of any generic concentrator-receiver system with high-pressure heat transfer fluid, with the objective of minimizing thermal losses.

Air Entrainment and Outlet Temperature Characteristics of a Modified Infrared Suppression Device With Inward and Outward Guides

AbstractA passive infrared suppression (IRS) device is an important and integral part of the modern naval/cargo ships, fighter jets, and helicopters to cool down the hot exhaust gas to suppress the infrared (IR) signatures. A modified IRS device has been proposed by putting inward/outward guides. The air entrainment and temperature ratios of the new type IRS device have been investigated by solving transport equations (continuity, momentum, energy, and turbulence) using the finite volume solver in ansys fluent. The Reynolds number (Ren), guide lengths (Lg/Dn), the inclination angle of guides (θg), overlap-height (Hov/Dn), and outlet temperature ratio (Tout/T∞) have been varied in the range of 1.5 × 10–1.5 × 106, 0–0.326, 0–75 deg, −0.326–0.018, and 1.243–2.576, respectively. It has been observed that the dimensional air entrainment increases with the Reynolds number and inlet temperature. The guide length alters the flow inside the IRS device and affects the entrainment ratio. We observed that, at the optimal value of guide length (Lg/Dn = 0.163) and inclination angle (θg = 15 deg), the IRS device entrains the maximum air, and attains a minimum temperature at the outlet. The mass suction and the outlet temperature of two different types of IRS devices have also been compared to choose the best one for the practical engineering application. An empirical correlation equation for air entrainment has been developed using nonlinear regression analysis.

Experimental Investigations on the Performance of a Hollow Fiber Membrane Evaporative Cooler (HFMEC) in Hot-Dry Regions.

The applicability of a hollow fiber membrane evaporative cooler in hot–dry regions was investigated by experimental studies. To better understand the actual operating environment of the hollow fiber membrane evaporative cooler, the outdoor air design conditions for summer air conditioning in five cities were simulated by an enthalpy difference laboratory. Subsequently, the effects of water and air flow rates on outlet air parameters and performance parameters were investigated by setting-up a hollow fiber membrane evaporative cooling experimental rig. It was found that the hollow fiber membrane evaporative cooler has good application prospects in hot–dry regions such as Lanzhou, Xi’an, Yinchuan, Urumqi, and Karamay. Among them, the hollow fiber membrane evaporative cooler has higher applicability in regions with higher air temperatures and lower humidity such as Urumqi and Karamay. The results indicate that the air outlet temperature and relative humidity ranged from 26.5 °C to 30.8 °C and 63.5% to 82.8%, respectively. The outlet air temperature and relative humidity of the HFMEC can meet the thermal comfort requirements of hot–dry regions in the summer at an appropriate air flow rate. The maximum air temperature drop, wet-bulb efficiency, cooling capacity, and COP were 7.5 °C, 62.9%, 396.4 W, and 4.81, respectively. In addition, the effect of the air flow rate on the performance parameters was more significant than that of the water flow rate.

Spray drying of avocado pulp using the seed as an adjuvant

Avocado, a native fruit from Mexico and Central America, is found in almost all tropical countries and consists of peel, pulp and seed. Avocado is a complementary food containing many lipophilic phytochemicals and bioactive compounds that may confer health benefits. The avocado seed represents 10% to 25% of its entire weight, depending on the fruit variety. It is a compelling source for creating new products because it is one of the best sources of dietetic fibre, with substances like fatty acids and antioxidants. However, in 2017, about 42,600 t of seeds were discarded in Brazil. Moreover, there are other problems and limitations to the use of avocado due to its low acidity and high perishability under environmental conditions. Therefore, it is necessary to employ conservation techniques to increase its shelf life. The avocado drying process has been studied, and the results show that avocado powder can potentially be used in the food, pharmaceutical and cosmeceutical industries, among others. This study aimed to assess the drying process of avocado pulp in a spray dryer, using the flour of its seed as an adjuvant to add value to that residue. The influence of outlet air temperature (90 °C – 110 °C) and seed flour concentration in the drying paste (0.0%–3.0% w/w) on the process yield and moisture content were evaluated using a factorial design. Furthermore, the paste and powders were chemically and physically characterised. The best drying condition was under an outlet air temperature of 110 °C and 3.0% seed flour concentration. That process combined the highest process yield (50%) with a low-moisture level of 1.25% and a low-water activity powder of 0.29. The use of the seed favoured the process yield compared with maltodextrin, showing that seed flour can be employed as an adjuvant in drying. The flowability of the powder was classified as cohesive, and the instant properties were poor. However, the avocado powder showed a similar protein, ash, lipids and carbohydrates content compared to the drying paste, making the product as nutritious as the fresh fruit. Additionally, it is a product with a high fibre content (10.47 g/100 g). The results suggest that avocado powder can be used as an ingredient for developing healthy food formulations, such as confectionery and bakery products. Special attention must be given to masking any bitter taste that may arise. • Avocado pulp drying was successful in adding value to a residue. • Potential utilization of avocado seed flour as an adjuvant in the pulp drying. • Process yield using avocado seed flour was higher than with maltodextrin. • The powder obtained in the best condition was as nutritious as the fresh pulp. • Avocado powder can be used as an ingredient for developing food formulations.

Investigation of an innovative Canadian well system combined with a frozen water/PCM heat exchanger for air-cooling in hot climate

In recent years, due to many reasons, such as environmental and economic problems, the use of shallow geothermal as a clean energy source has been of great interest inside the scientific community. However, the main targeted application is air cooling and heating in buildings by using a buried pipe in the ground known as Earth to Air Heat Exchanger (EAHE). This system (EAHE) alone cannot fulfill the comfort conditions in countries characterized by hot and cold climates, and an auxiliary system is required. The present work proposes a new hybrid system consisting of coupling the EAHE (primary system) with a concentric two pipes heat exchanger (secondary system). The inner pipe has multiple longitudinal fins filled with frozen water or a mixture of ethylene glycol and water as a phase change material (PCM). The air is cooled when exchanging heat with a frozen PCM in the secondary heat exchanger (Water/PCM HEX). A theoretical investigation of the proposed hybrid system has been carried out. However, transient models have been developed for both heat exchangers, and the nonlinear equations obtained have been solved using numerical methods. The simulation of the behavior of this hybrid system located in Madinah city (Kingdom of Saudi Arabia), presenting a hot climate, has been carried out. The effect of geometrical parameters and operation conditions on the outlet air temperature and the operation period has been investigated. The study results show that the convective heat transfer coefficient is significant in the Water/PCM HEX. As long as its value is low, the cooling is not significant; as shown by decreasing the freezing temperature from 0 °C to −10.71 °C, the gain in the outlet air temperature dropping is <1 °C. When the external pipe diameter has been reduced from 8 to 6 in., the air is cooled down by almost 5 °C. The proposed system presents an attractive cooling solution during peak periods, especially for hot climates less severe than Madinah.

Critical evaluation of the thermal performance analysis of a new cooling tower prototype

This paper presents a critical evaluation of the thermal performance analysis of the inverted cooling tower, which was conceived as a new cooling tower prototype that prevents the dispersion of pollutants to the atmosphere during its operation. The device can be classified as a mechanical forced draft, counterflow-parallel flow cooling tower. The combination of the Merkel and Poppe methods of analysis and the counterflow, parallel and counterflow/parallel flow arrangements has been discussed, for a total of 5 different approaches. The Poppe method for thermal performance prediction reports higher Merkel numbers than the Merkel method: from 3.84% to 6.64%. A higher Merkel number is obtained for the parallel arrangement compared to counterflow to achieve the same cooling. Differences from 1.12% to 12.19% are observed for the range of tested water-to-air mass flow ratios. The rigorous method that uses the Poppe theory and combines counterflow and parallel flow arrangements (main novelty of this paper) is recommended to evaluate the thermal performance. Not only it provides the best predictions for the outlet water and air temperatures (0.44 °C difference for the water prediction and 0.74 °C difference for the air) but it is a good approximation of the complex underlying physics of the problem and the state of the outlet air is accurately determined. • A critical evaluation of the performance of a novel cooling tower was conducted. • The Poppe theory combining parallel/countercurrent flow arrangements is suggested. • The method predictions are confident: less than 2% for water and air temperatures. • The Poppe theory reports results 3.76% and 6.67% higher than the Merkel theory. • Parallel configuration provides up to 12.26% higher Merkel number than counterflow.

Experimental and numerical investigation of a counter-flow hollow fiber membrane-based evaporative cooler

A counter-flow hollow fiber membrane-based evaporative cooler (HFMEC) was proposed. An experimental setup was developed to investigate the air handling performance of the HFMEC under various operating conditions. A numerical model was established and validated. The outlet air temperature predicted by the numerical model using free surface model showed a maximum deviation of 5% comparing with the experimental data. The model was further used to conduct a parametric analysis of the HFMEC. Six key parameters, including geometric specifications and operating conditions, were selected as factors for the sensitivity analysis. The cooling capacity and coefficient of performance (COP) were chosen as performance evaluation indicators. The simulation was performed with 27 cases for the orthogonal test. The range analysis revealed that the inlet air relative humidity and velocity, as well as packing fraction had significant impact on its cooling capacity and COP. Ranking the influence degree of key design parameters on performance evaluation indicators, this paper provides a convenient method to design and optimize the counter-flow HFMEC.

Performance improvement methods for quartz tube solid particle fluidized bed solar receiver

The conditions to improve performance of quartz tube silicon carbide (SiC) solid particle fluidized bed solar receiver was investigated with computational fluid dynamics (CFD) simulations. The difficulty of experimenting all possible operating conditions was overcome by preparing CFD base input with appropriate models and parameters. The amount of SiC in the bed, the size of particles, and the air inlet velocity were considered as variables. After model verification, in order to evaluate the effect of particle addition, bed without solid particles were simulated first. Outlet temperature of single-phase receiver was calculated as 421 K. Outlet temperatures of 913 K, 895 K, and 881 K were obtained for 400 μm diameter particles in 0.3 m bed height for air inlet velocities of 0.25, 0.3, and 0.35 m/s. Air outlet temperature decreases as air inlet velocity increases. On the other hand, too much reduction at inlet velocity retards the system performance since it affects fluidization. For 400 μm particle diameter and bed height of 0.2 m, outlet temperatures of 994 K, 974 K, and 955 K were found for the same air inlet velocities above. As bed height decreases, air outlet temperature increases. For particle diameters of 300 and 500 μm for bed height of 0.3 m, outlet temperatures of 980 K and 878 K were calculated for appropriate minimum fluidization velocities. Outlet temperature increased with decreasing particle size.

Investigation of a novel window solar air collector with 7-moveable absorber plates

The focus of this paper is on a thermal performance of the window solar air collector with seven-moveable circular perforated absorbent plates that controlled manually. The proposed window solar air collector is a solar thermal system which can be employed to preheat the ventilation air supply and compromise between sunlight penetration to the desired buildings and hot air gain. In this work, five angles are selected (0 °, 30 °, 45 °, 60 °, and 90 °) and mathematical model and formulation based on the finite volume scheme (SIMPLE) algorithm has been implemented to solve the 3-D forced convection with turbulent flow. Different values of solar irradiance intensities (330, 530, and 730 W/m2) and air mass flow rates (0.0097, 0.0151, 0.0224, and 0.0298 kg/s) were adopted. The results found significant difference between air inlet and outlet temperatures are gained at angle 0° (vertical absorbent plates position) at irradiance 730 W/m2 and mass flow rate 0.0097 kg/s is 11.2 °C and the maximum thermal efficiency is 71% at a mass flow rate of 0.0298 kg/s. Also, flexibility between hot air from the collector and sunlight penetrating into the room is gained when the plate angles set on (30 °, 45 °, 60 °, and 90 °).