Tubular Air Research Articles

A Regenerative Coking‐resistant CO2 Hydrogenation Reactor using a Protonic Ceramic Electrolysis Cell with Thin and Robust Fuel Electrode

AbstractA CO2 hydrogenation reactor based on protonic ceramic electrolysis cells (PCECs) is one of the most promising options for the efficient and clean conversion of CO2. However, insufficient performance and durability have hindered the practical application of such CO2 hydrogenation reactors. Here, fabricates a large‐area (≈10 cm2) tubular air electrode supported PCEC (AES‐PCEC) and develop a fuel electrode regeneration strategy for efficient and durable CO2 hydrogenation. The AES‐PCEC demonstrates a CO yield of 2.88 mL min−1 at 650 °C while maintaining excellent durability for over 1100 h. The high stability of the AES‐PCEC can be attributed to the robust and thin fuel electrode structure as well as the water‐mediated carbon removal regeneration mechanism. Density functional theory calculations have confirmed the regeneration mechanism facilitated by the excellent water hydration and dissociation capability of the BaCe0.4Zr0.4Y0.1Yb0.1O3‐σ. This work offers a feasible strategy to design high‐performance and durable PCEC‐based CO2 hydrogenation reactors.

Design, Simulation and Optimization of a Novel Transpired Tubular Solar Air Heater

In this paper, a novel tubular solar air heater is introduced. In this air heater, the hot boundary layer is drawn into the absorber tube and can provide thermal energy at moderate temperatures. Several different cases were simulated and a correlation was proposed to predict the collector’s effectiveness as a function Rayleigh number and Reynolds number. An equation was derived to find the effectiveness of this collector. Finally, a real case was studied with non-uniform solar flux distribution, as well as radiation heat loss. Good agreement was found between the results and those derived by the proposed analytical method. For different suction values, the first-law and the second-law efficiencies were calculated. Based on the exergy analysis, exergy destruction in absorption is the dominant factor that is unavoidable in low-temperature collectors. It was shown that there is an optimum suction value at which the second-law efficiency is maximized. At the optimum point, temperature rise can reach 54 K, which is hardly possible with a flat plate collector. Based on the exergy analysis, the relation between tube wall temperature and air outlet temperature in their dimensionless forms at the optimum working condition was derived, and it was shown that effectiveness at the optimum working condition is around 0.5. This means that the air temperature rise shall be half of the temperature difference between collector wall and the ambient temperatures. A high outlet temperature besides the low cost of construction and maintenance are the main advantages of this air heater. With such a high temperature rise, this type of collector can increase the use of solar energy in domestic applications.

CFD modeling of a tubular three-pass solar air heater with phase change material: Investigating heat transfer enhancement and energy efficiency

The present study introduces a novel solar air heater design featuring a tubular surface with three passes arranged in a counter-flow configuration, aimed at improving compactness and enhancing heat transfer characteristics. The research involved the development and validation of a computational fluid dynamics (CFD) model, which was utilized to accurately depict the distribution of solar flux through the system components by comparing the model results with experimental data. The study involved conducting a comparative analysis between the tubular three-pass solar air heater with phase change material (TTPSAH_PCM) and conventional flat plate solar air heaters (FPSAH) to ascertain the superior design characteristics. A thorough investigation was carried out, encompassing evaluations of energy, exergy, outlet temperature, convection heat transfer coefficient, and useful heat gain. The findings indicate that the TTPSAH_PCM outperforms alternative geometries. For instance, when operating at a mass flow rate of 0.006 kg/s, the TTPSAH_PCM demonstrates substantial enhancements in several key metrics, including an 11.4 % increase in the system's daily thermal efficiency, a 17 % improvement in exergy efficiency, and a 4 % rise in outlet air temperature. The convection heat transfer coefficient of TTPSAH_PCM exhibited a 155.6 % increase compared to the FPSAH type. Moreover, the system being investigated demonstrates an 8.5 % rise in useful heat gain. The results underscore the enhanced efficacy of the TTPSAH_PCM system in contrast to alternative solar air heater arrangements, and its applicability for both drying operations and indoor heating applications.

Assessing the effects of different finned absorbers with swirl flow on the performance of solar air heater

ABSTRACT In this study, the effects of various absorber configurations of a tubular solar air heater are investigated. The models such as direct flow with a standard absorber (DF-SA), swirl flow with a standard absorber (SF-SA), swirl flow with perforated longitudinal fins (SF-PLF), swirl flow with radial fins (SF-RF), swirl flow with perforated radial fins (SF-PRF) are studied. Investigation parameters including Nusselt number, exergy efficiency, PEC, and friction factor are examined with Reynolds numbers ranging from 8488 to 25,464. The findings reveal an enhancement in Nusselt number, PEC, and exergy efficiency corresponding to an increase in Reynolds numbers, while the friction factor decreases. Models employing air-swirl flow entrances demonstrate superior effects in improving the performance compared to direct flow inlets. Notably, the SF-PRF shape records the maximum Nu ratio of (102.5–108%). This model has the maximum values of PEC enhancement ratio of (103.9–106.2%) compared to DF-SA, indicating the enhancement obtained by using swirl flow with perforated ring fins. Analysis of streamlines and distributions of temperature, pressure, and velocity elucidates the effects of perforated radial fins on vortex generation and secondary flow, particularly when incorporating air swirl inlets.

Experimental and numerical investigation of porous heat exchangers with Kelvin cell structured foam at high temperatures: Coupled conduction-convection and radiation heat transfer

Heat recovery is crucial in the energy sector, especially for industries operating at high temperatures. One way to achieve high-efficiency heat recovery is to use porous materials in heat exchangers. In this work, the performance of a high temperature heat exchanger was investigated. For this purpose, a tube containing a porous cast iron structure was externally heated by radiation inside a tubular furnace and air at ambient temperature was blown into the tube. Experiments were conducted at different temperatures of up to ▪ and different airflow velocities in a specialized bench, considering the combined effects of conduction, convection, and radiation. Temperature profiles in three sections of the porous structure were measured by using sheathed thermocouples brazed to the porous structure. Power and exergy flow rate extracted from the porous structure to the air flow were calculated and analyzed to quantify recovered heat. In addition, a numerical modeling performed at the pore level using Fluent showed an average relative error of 15% compared to experimental results, indicating acceptable agreement with observed trends. This numerical model will serve as a valuable reference tool for future parametric analyses of porous structures in heat exchanger configurations.

Numerical Simulation of the Thermal Performance of a Tubular Solar Air Heater

In this work, a flat-plate solar air heater (FSAH) and a tubular solar air heater (TSAH) were designed and tested numerically. The work investigates the effect of increasing the contact area between the flowing air and the absorber surface of each heater and predicts the expected results before the fabrication of the experimental rig. Three-dimensional two models were designed and simulated by the ANSYS-FLUENT 16 Program. The solar irradiation and ambient air temperature were measured experimentally on December 1st 2022, at the weather conditions of Baghdad City- Iraq, at three air mass flow rates, 0.012 kg/s, 0.032 kg/s, and 0.052 kg/s. The numerical results showed the advantage in the thermal performance of the TSAH in comparison to the FSAH, represented by better air temperature difference, better heat transfer from the absorber to air, and better thermal efficiency. The TSAH has a higher thermal efficiency than the FSAH by 7 %, 19 % °C, and 22 % at 0.012 kg/s, 0.032 kg/s, and 0.052 kg/s, respectively. The improvement of the thermal characteristics of the TSAH can be referred to as the increment in the heat transfer contact area between the absorber and the flowing air.

Experimental and numerical methods for the performance analysis of a tubular three-pass solar air heater

A new absorber surface is designed for solar air heaters to make them compact and enhance heat transfer parameters. The current paper presents the novel absorber design using a tubular surface having three-pass in counter-flow. The absorber tubes are constructed from thin sheets of aluminium; 15 tubes are closely spaced in line with each other to establish three-pass, i.e. five tubes per pass. The research paper investigates numerically and experimentally the thermo-hydraulic performance of a Tubular Three-pass Solar Air Heater (TTPSAH). The numerical model was developed using MATLAB to predict the performance and outlet air temperature. The error in numerical and experimental evaluation is approximately 5%, showing promising results. It was found that the TTPSAH accelerates heat transfer in a compact surface area. The maximum thermal efficiency was evaluated as 60.04%, 41% and 33.3% for an airflow rate of 0.006 kg/s, 0.004 kg/s, and 0.002 kg/s respectively. Thermal enhancement with a maximum outlet air temperature of 110.6 °C, 91.4 °C and 80.2 °C was recorded at a mass flow rate of 0.002 kg/s, 0.004 kg/s and 0.006 kg/s in glazed conditions. Furthermore, the research includes an estimation of the energy cost per kilowatt-hour (kWh), which amounts to $0.017, $0.025, and $0.0311 for mass flow rates of 0.006 kg/s, 0.004 kg/s, and 0.002 kg/s, respectively.

Energy and exergy evaluation of new design nabla shaped tubular solar air heater (∇ TSAH): Experimental investigation

Energy and exergy evaluation of new design nabla shaped tubular solar air heater (∇ TSAH): Experimental investigation

Finned Tubular Air Gap Membrane Distillation.

Finned tubular air gap membrane distillation is a new membrane distillation method, and its functional performance, characterization parameters, finned tube structures, and other studies have clear academic and practical application value. Therefore, the tubular air gap membrane distillation experiment modules composed of PTFE membrane and finned tubes were constructed in this work, and three representative air gap structures, including tapered finned tube, flat finned tube, and expanded finned tube, were designed. Membrane distillation experiments were carried out in the form of water cooling and air cooling, and the influences of air gap structures, temperature, concentration, and flow rate on the transmembrane flux were analyzed. The good water-treatment ability of the finned tubular air gap membrane distillation model and the applicability of air cooling for the finned tubular air gap membrane distillation structure were verified. The membrane distillation test results show that with the tapered finned tubular air gap structure, the finned tubular air gap membrane distillation has the best performance. The maximum transmembrane flux of the finned tubular air gap membrane distillation could reach 16.3 kg/m2/h. Strengthening the convection heat transfer between air and fin tube could increase the transmembrane flux and improve the efficiency coefficient. The efficiency coefficient (σ) could reach 0.19 under the condition of air cooling. Compared with the conventional air gap membrane distillation configuration, air cooling configuration for air gap membrane distillation is an effective way to simplify the system design and offers a potential way for the practical applications of membrane distillation on an industrial scale.

Carbon spheres modified titanium air diffusion cathode for boosting H2O2 and application in disinfection

In situ electrochemical disinfection via H2O2 through two-electron molecular oxygen reduction reaction (2e-ORR) represents a promising strategy for sustainable disinfection. However, its disinfection performance is largely confined by its low selectivity/reactivity towards two-electron oxygen reduction reaction (2e-ORR) for H2O2 production. To tackle this, carbon spheres modified tubular titanium air diffusion cathode (CS@TTC) was developed. It intended to improve interfacial structures for high H2O2 production through a facile hydrothermal carbonation approach. Evolution of morphology and chemical nature of carbon spheres have been systemically investigated under diverse hydrothermal temperature, hydrothermal time and pyrolysis temperature·H2O2 accumulation has improved 6.59-fold at CS@TTC compared to the raw base TTC. Both chemical nature of carbon sphere and a superior oxygen mass transfer (0.0284 s−1) were responsible for this enhancement. Besides, CS@TTC cathode was used in the electrochemical system for disinfection performance, in which 6.42 log of E. coli was deactivated after 120 min. Hence, this study gives an insight into that the H2O2-based electrochemical disinfection is promising to be a next-generation process.

Experimental evaluation of the performance of newly designed tubular SAH with infinity (∞) shaped inner tubes

A new design of tubular solar air heater (SAH) is examined experimentally in this work. The SAH absorber consists of one row of adjacent equal tubes forming flat pack. Each tube contains two adjacent inner tubes, the diameter of each of which equals the radius of the outer tube. The two inner tubes form the shape of infinity (∞), therefore, the new design is expressed as infinity shaped tubular SAH (∞TSAH). The performance of the ∞TSAH is examined against ordinary tubular SAH (OTSAH)) having tubular absorber consists of one row of only adjacent equal tubes. The comparison is performed at different mass flow rates of the air (MFRs) and under single pass flow (SPF) and double pass flow (DPF) of the air. The findings show clearly that the output air temperature, energy efficiency and thermohydraulic efficiency, of ∞TSAH are better than that of OTSAH. The maximum output air temperature rise is about 47.1 °C and 37.1 °C for ∞TSAH and OTSAH, respectively at MFR of 0.017 kg/s and DPF condition. In addition, the ∞TSAH achieves maximum energy efficiency of 84.5% at MFR of 0.079 kg/s and DPF condition with percentage increment of 8.4% relative to OTSAH which achieves energy efficiency of 77.3% at the same condition. Moreover, the ∞TSAH achieves maximum thermohydraulic efficiency of 79% at MFR of 0.052 kg/s and DPF condition, while OTSAH achieves a value of 72.6% at MFR of 0.079 kg/s and DPF condition.

Experimental Evaluation of Thermohydraulic Performance of Tubular Solar Air Heater

The thermohydraulic performance of a new design solar air heater (SAH) design was examined experimentally in this paper as a trial to improve the flat-plate SAH’s efficiency. A flat-plate solar air heater (FPSAH) and a jacketed tubular solar air heater (JTSAH) having similar dimensions were constructed to compare their thermal performance efficiencies. A band of Aluminum jacketed tubes were arranged side by side in parallel to the airflow direction to form the absorber of a jacketed tubular solar air heater (JTSAH). The experiments were accomplished at three mass flow rates (MFR)s: 0.011 kg/s. 0.033 kg/s, and 0.055 kg/s. Results revealed that the maximum temperature difference was obtained from JTSAH at 38°C in comparison to 32°C from the FPSAH at MFR of 0.011 kg/s. The thermal losses from the upper glass cover of the JTSAH were less than the same losses at the FPSAH due to the reduced absorber and glass temperatures of the JTSAH. The gained power was higher at the JTSAH than the FPSAH. At the JTSAH, at 0.055 kg/s MFR, the maximum average thermal efficiency obtained was 81%, and the maximum average thermos-hydraulic efficiency obtained was 75.61 %. It is noted that increasing the MFR increases the thermal efficiency, also, its optimum value rises the thermos-hydraulic efficiency to a specific optimum point. The pressure drop increases with the MFR and JTSAH compared to the FPSAH

SO3 Migration and Emission Characteristics of CFB Boilers

In order to study the migration and transformation of SO3 from circulating fluidized bed boiler (CFB) in the air preheater and flue gas treatment facilities, 10 circulating fluidized bed boilers with installed capacities between 150 MW and 330 MW were measured by controlled condensation method. Ten circulating fluidized bed boilers with installed capacities ranging from 150 MW to 330 MW were measured using the controlled condensation method. It is showed that the SO3 removal rate of the air preheater was affected by the air preheater flue gas exit temperature, which ranged from 6.7 % to 36.5 %, and the SO3 removal rate of the rotary air preheater was higher than that of the tubular air preheater. The SO3 removal rate of cloth bag filter and electric bag filter is above 40 %; the SO3 removal rate of electrostatic precipitator is between 6.1 % and 10.8 %. The SO3 removal rate of wet desulfurization method ranges from 41.7 % to 73.4 %, with the highest SO3 removal rate of double tower double cycle. The SO3 removal rate of off-furnace CFB semi-dry desulfurization reached 89.7 %~97.9 %, and the dry process inside the furnace + off-furnace CFB semi-dry process could reduce the SO3 at the desulfurization outlet to below 0.3 mg/m3 under the tested conditions. The conclusions of the test analysis in this paper can provide reference for SO3 control in circulating fluidized bed boilers and related policy formulation.

Simulation of particle interception of seamless knitted composite filter material based on the discrete phase model

In this research, a three-dimensional geometric model of knitted cylindrical air filter material is constructed. Due to the isotropy of the three-dimensional structure, a certain cyclic structure is selected for the flow calculation domain in this research. According to the principle of air filter particle testing, the pressure drop of the filter material and the particle collection efficiency are simulated and calculated. Applying ANSYS finite element analysis software, based on Fluent's fluid Lagrangian discrete model, the geometric model is meshed and the particle materials and boundary conditions are set. Air is the continuous phase, and its velocity is set at 0.27 m/s. The jet particles are used as discrete phases to track the particle trajectory in real time. Based on the above conditions, the simulation of the capture efficiency of weft-knitted tubular air filter material for different particle sizes can not only predict and evaluate the filtering efficiency of the knitted tubular air filter material, but also provide a theoretical reference for fluid simulation of the knitted filter material.

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.

Tubular solar air heater using finned semi-cylindrical absorber plate with swirl flow: Experimental investigation

In this research, a tubular swirl-flow solar air heater (SF-SAH) with a find semi- cylindrical absorber plate is adopted to enhance its thermohydraulic performance. The proposed SF-SAH is tested with two types of fins: radial and longitudinal. Three sets of fins; 3, 4, and 5number of fins are tested. Data obtained from the proposed SF-SAH are compared with the plain duct conventional SF-SAH without fins under a typical air flow rate range 0.01–0.050 kg/s and Reynolds number (Re) from 7078 to 35190. Results obtained from this study reveal that radial fins enhance SF-SAH performance parameters when compared with the plain heater or heater with longitudinal fins. Also, increasing the number of radial fins and air flow rate enhances SF-SAH efficiency and Nusselt number and reduce the production cost. SF-SAH with five radial fins and air flow rate of 0.050 kg/s results maximum values for thermal and thermohydraulic efficiencies of 76.79%, 72.40%, respectively, Nusselt number of 223.64, and a minimum estimated production cost of 0.0105 $/kW.hr. The maximum effectiveness and exergy efficiency of SF-SAH are obtained with five radial fins and reached about 0.6 and 1.3 % respectively.

INFLUENCE OF CONTAMINATION OF LOW-TEMPERATURE HEATING SURFACES OF BOILER ON THE INTENSITY OF CONVECTIVE HEAT EXCHANGE DURING THE BURNING OF NON-DESIGN FUEL

The study of the influence of the degree of contamination of low-temperature heating surfaces on the intensity of convective heat transfer during the burning of non-design fuel based on computer modeling has been carried out. The results of the analysis showed that the amount of deposits varies depending on the temperature of the heat carriers in the air heater. A new method for calculating the thermophysical parameters of the heat transfer process has been developed on the basis of the ANSYS software package, which makes it possible to obtain a complete description of complex heat transfer processes in the boiler air heater. In the developed computational three-dimensional thermophysical model of a recuperative tubular air heater, there is no tube wall, the created thermal resistance of the wall is taken into account by introducing the coefficient of effective thermal conductivity of the flue gas flow.

Long-term evaluation of an air-cathode microbial fuel cell with an anion exchange membrane in a 226L wastewater treatment reactor

Although the treatment of municipal wastewater using microbial fuel cells (MFCs) has been extensively studied, scaling the systems up for practical use remains challenging. In this study, a 226 L sewage treatment reactor was equipped with 27 MFC units, and its chemical oxygen demand (COD) removal and electricity production were evaluated. The MFC units were tubular air cores with a diameter of 5 cm and length of 100 cm, which were wrapped with a carbon-based cathode, anion exchange membrane (AEM), and nonwoven graphite fabric. The air-cathode–AEM MFC generated 0.12–0.30 A/m2, 0.072–0.51 W/m3, and 1.7–4.6 Wh/m3 in a chemostat reactor with a COD of 140–36 mg/L and hydraulic retention time (HRT) of 9–42 h throughout a year. The decrease in the COD was represented as the first-order rate constant of 0.038. The rate constant was comparable to that of other air-cathode MFCs with cation exchange membranes, indicating the necessity of a posttreatment to meet the discharge standard. It has been estimated that the MFC operation for 24 h before post-aeration can reduce the energy required to meet the discharge standard by 70%, suggesting the potential applicability of MFC in long HRT-treatments such as oxidation ditch. The resistances of the anode, cathode, and AEM were 15, 7.0, and 0.51 mΩ m2, respectively, and surface dirt rather than deterioration primarily increased the AEM resistance. A current exceeding 0.2 A/m2 significantly increases the anode potential, indicating that the current was limited by low COD. Increasing the anode-specific surface area can improve air–AEM MFCs used for practical applications.

Microalgae hydrogel-derived monolithicfree-standing air cathode for microbial fuel cells: Tailoring the macroporous structure for enhanced bioelectricity generation

A high-performance and cost-effective cathode is highly desirable for the practical implementation of microbial fuel cell (MFC) technology, used for renewable energy recovery from wastewater. In this study, a monolithic, free-standing air cathode for MFCs is fabricated through a sol-gel-based route. Chlorella pyrenoidosa (CP) is selected as the catalyst precursor, polyacrylonitrile fiber as the precursor for the conductive and supporting skeleton, and deionized water as the solvent and pore former. Agar is also used as the gelling agent to facilitate the formation of 3D porous networks inside the cathodes. By systematically tailoring the porosity of the tubular air cathodes by varying the water content in the CP agar composite hydrogel, the mechanical strength and electrical conductivity of the cathode is optimized. Moreover, this fabrication process leads to abundant active sites for the oxygen reduction reaction and an interconnected hierarchical porous structure with separated transport paths for air supply and ion transfer. The tubular air cathode can be directly employed as an MFC cathode without the use of a polymer binder or other modifications. The MFC delivers a maximum power density of 106.3 ± 5.9 W m-3, which is approximately 33% higher than that with a converntional Pt/C cathode (79.8 ± 4.1 W m-3). This work therefore offers a promising new route for recovering bioelectricity from wastewater based on MFCs.

Energy, exergy, and economic analysis of tubular solar air heater with porous material: An experimental study

• Solar air heater having new designed tubular absorber is examined experimentally. • Assessment of the new tubular air heater with porous medium is presented. • Using porous material with tubular heater enhances its energy efficiency by 8.9% • Using porous media with tubular heater enhances its exergy efficiency by 8.2% • Tubular air heater is more effective compared to flat one based 4E analyses. The performance of solar air heater of having a new design tubular absorber of adjacent parallel tubes called tubular is investigated experimentally via energy, exergy, energy payback time, exergoeconomic, and enviroeconomic approaches. Moreover, the impact of utilizing porous material on the tubular heat performance is analyzed and compared to flat plate air heater at air mass flow rates; 0.075, 0.05, and 0.025 kg/s for single and double passes. Results indicate that the tubular heater has higher net energy gain, output air temperature, energy and exergy efficiencies, and smaller energy loss compared to the flat heater. Using porous material and double pass increases the output air temperature of tubular air heater by 3.4 °C and flat one by 17.7 °C at 0.025 kg/s. Moreover, utilizing porous material with the tubular heater at 0.075 kg/s enhances the energy efficiency by 3.5% and 8.9% and exergy efficiency by 8.2% and 0.9% for single and double pass, respectively. Air pumping power of the tubular heater is greater than flat but its value is very small to influence the tubular net useful energy. Finally, the tubular air heater is more effective compared to flat based on energy payback time, energy cost, exergoeconomic, and enviroeconomic parameters.