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Hirofumi Daiguji - One of the best experts on this subject based on the ideXlab platform.
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theoretical analysis of transient heat and mass transfer during Regeneration in multilayer fixed bed binder free desiccant dehumidifier model validation and parametric study
International Journal of Heat and Mass Transfer, 2019Co-Authors: Jubair A Shamim, Soumyadeep Paul, Kenji Kitaoka, Weilun Hsu, Hirofumi DaigujiAbstract:Abstract A numerical model is presented for the prediction of transient heat and mass transfer characteristics during the Regeneration process in a multilayer fixed-bed, binder-free desiccant dehumidifier. Experiments were carried out in a previous study that provided the benchmark data for validation of the current model under different temperatures and velocities of the Regeneration Air. A spherical microsphere silica gel having a pore diameter of 2.7 nm was used as the adsorbent during the experiments. In the first part of this study, model validation was performed for different temperatures (314.4–325.0 K) and velocities (0.6–0.9 m s−1) of Regeneration Air. The results showed that at a fixed Regeneration temperature (325.0 K), the model predicted mass of the desorbed water as well as the desiccant bed and Air temperatures were in a good agreement with the previously reported experimental results. With a decrease in the temperature and velocity of the Regeneration Air, the model slightly underpredicted the experimentally obtained mass of the desorbed water; however, the deviation remained within a reasonable limit. Upon validation, a parametric study was carried out to show how the heat and mass transfer characteristics of the microsphere silica gel during desorption depended on the intrinsic material properties (e.g., desorption rate constant, diffusivity, and desorption isotherm) and mechanical design parameters of the device (e.g., convective heat transfer coefficient, porosity, and thickness of the desiccant bed).
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experimental evaluation of transient heat and mass transfer during Regeneration in multilayer fixed bed binder free desiccant dehumidifier
International Journal of Heat and Mass Transfer, 2019Co-Authors: Jubair A Shamim, Soumyadeep Paul, Kenji Kitaoka, Weilun Hsu, Hirofumi DaigujiAbstract:Abstract In this study, Regeneration experiments were performed in a previously developed multilayer fixed-bed, binder-free desiccant dehumidifier (MFBDD) in order to investigate the transient heat and mass transfer characteristics during the desorption of condensed water from desiccant material inside the device. A microsphere silica gel (M.S.GEL manufactured by AGC Si-Tech. Co., Ltd., Japan) having a pore diameter of 2.7 nm was used as the desiccant, which was feasible for Regeneration at a temperature slightly above 50 °C. To prevent heat loss during Regeneration, the test section was placed inside a constant-temperature oven. Experiments were performed under several Regeneration conditions to investigate the influence of temperature, humidity, and flow velocity of the Regeneration Air on the heat and mass transfer characteristics of the device. The influence of heat loss from the test section to the surroundings during Regeneration was also determined by precisely controlling the oven temperature. The results revealed that the Regeneration capacity of the device improved with an increase in the Regeneration Air temperature. However, the maximum temperature of Regeneration Air should be optimized for energy-efficient operation of the device according to the Regeneration conditions.
Akio Kodama - One of the best experts on this subject based on the ideXlab platform.
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Separation and enrichment of CH_4 and CO_2 from a dry biogas using a thermally regenerative adsorbent-packed heat exchanger
Adsorption, 2019Co-Authors: Nur Izdiharr Zainol, Takuya Tsujiguchi, Yugo Osaka, Mikio Kumita, Akio KodamaAbstract:Thermal swing adsorption (TSA) using a heat exchanger packed with an adsorbent material was examined as a means of removing CO_2 from a simulated biogas. TSA driven by low-temperature waste heat or solar energy represents an environmentally-friendly gas separation process. In this process, the adsorbent material can be heated indirectly by circulating hot water through a heat exchanger and can operate with a smaller amount of Regeneration Air than in a conventional TSA system to significantly increase the CO_2 concentration at the Regeneration outlet. In the present work, carbon molecular sieves (CMS) and a high-silica zeolite (HSZ) were examined with regard to their CO_2 adsorption from a simulated biogas containing 60% CH_4 and 40% CO_2. The effects of the hot water temperature supplied to the adsorber and the Regeneration Air flow rate on the separation performance were investigated. Increasing the Regeneration temperature was found to improve the separation performance, and the HSZ was observed to be more selective for CO_2 during the adsorption process. However, the CO_2 concentration in the desorption outlet gas was not increased when the Regeneration Air flow was equal to that of the feed gas. Reducing the Regeneration Air flow rate to one-tenth the original value significantly increased the CO_2 concentration at the desorption outlet while only slightly lowering the CH_4 concentration in the product gas. A TSA process incorporating an adsorbent-packed heat exchanger is evidently an effective means of processing biogas, based on poor adsorption of CH_4 and strong adsorption of CO_2.
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Performance of VOC Abatement by Thermal Swing Honeycomb Rotor Adsorbers
Industrial & Engineering Chemistry Research, 2007Co-Authors: Hisashi Yamauchi, Akio Kodama, Tsutomu Hirose, Hiroshi Okano, Ken Ichiro YamadaAbstract:Fine powder of hydrophobic high silica zeolite was solidified with silica sol in the void of a 0.2 mm thick ceramic fiber sheet fabricated into a honeycomb structure, typically with 3.2 mm pitch × 1.7 mm height. The honeycomb rotor of adsorbent was applied to the VOC abatement system operating with thermal swing adsorption. Dependence of the removal efficiency of VOC on various variables was investigated for a test honeycomb rotor of 300 mm in diameter. The following operating guide was recommended to reach high performance where more than 95% of VOC in the feed gas is removed: superficial velocity of feed Air = 2−4 m/s, flow rate ratio of process to Regeneration zone = 5−15, relative humidity < 80%, and Regeneration Air temperature = 180 °C with rotation speed optimized. The optimal rotation speed of the honeycomb rotor was investigated closely, and the result was interpreted in terms of the heat capacity ratio between the honeycomb rotor and the Regeneration Air stream.
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Experimental Study on a Process Design for Adsorption Desiccant Cooling Driven with a Low-Temperature Heat
Adsorption, 2005Co-Authors: Kosuke Ando, Akio Kodama, Motonobu Goto, Tsutomu Hirose, Hiroshi OkanoAbstract:Among the desiccant cooling process, 2-rotor process consisting of a honeycomb rotor dehumidifier and a sensible heat exchanger is the mainstream of the cooling processes which are practically applied to supermarket, hospital and so on. Most of them are driven with a higher Regeneration temperature around 100–140^∘C obtained from gas-engine heat pump or micro gas turbine generator. However, dehumidifying performance of this typical configuration driven with a low temperature heat is not sufficient for cooling at higher ambient humidity. In this study, 4-rotor desiccant cooling process equipped with a double stage dehumidification was proposed and investigated experimentally. In this process, Regeneration temperature around 70^∘C could produce a sufficient dehumidifying performance at high ambient humidity. Furthermore, the cascade use of hot water inside the cooling cycle was applied and confirmed somewhat lower cooling performance than that operated with parallel supply of hot water. Against this result, COP_r of the former was much higher than that of the latter. Effect of water spray evaporative cooling at the inlet of Regeneration Air stream on the process performance was also investigated. This evaporative cooling was expected to cause humidity increase in Regeneration Air reducing the dehumidifying performance of the honeycomb absorber, while the evaporative cooling plays an important role to produce a lower temperature in supply Air. Experimental results showed that the amount of dehumidified water at the process without water spray evaporative cooler was actually larger than that of process with water spray evaporative cooler. This behavior was due to increase of humidity or relative humidity in the Regeneration Air as expected. However, temperature of supply Air produced by the process with evaporator was rather lower than that of the other, resulting higher COP value. It was concluded that the evaporative cooler effectively worked at higher Regeneration temperature and lower ambient humidity.
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The use of psychrometric charts for the optimisation of a thermal swing desiccant wheel
Applied Thermal Engineering, 2001Co-Authors: Akio Kodama, Motonobu Goto, Tsutomu Hirose, Tadashi Hirayama, Robert E. CritophAbstract:Abstract An effective prediction is proposed to estimate the optimal rotation speed and performance of a rotary adsorber, in which simultaneous enthalpy and humidity changes are dealt with separately by visualising changes of state of product or exhaust Air on a psychrometric chart. Assuming that the adsorbent rotor is completely regenerated to equilibrium with the Regeneration Air during the corresponding period, the optimal rotation speed corresponds to the region of the short time adsorption in which penetration theory holds and enthalpy exchange between both streams through the adsorbent rotor follows the behaviour of a rotary sensible heat exchanger at lower revolution rates. The change of the product/exhaust Air condition with increasing rotational speed is presented as a set of simple equations. Also, by considering the relative humidity of product Air and that of Regeneration Air to be almost the same at a sufficiently high flow rates of Regeneration Air, an optimal rotation speed and the product Air condition are easily found by simple calculation. In comparison with experiments, the proposed method gives a rotational speed near the “optimum” and the humidity and temperature of the product Air are predicted almost exactly.
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An Adsorptive Desiccant Cooling Using Honeycomb Rotor Dehumidifier
Journal of Chemical Engineering of Japan, 1998Co-Authors: Akio Kodama, Motonobu Goto, Tsutomu HiroseAbstract:A field-test of a 20 kW apparatus for adsorptive desiccant Air conditioning has been carried out at the Biochemical Engineering Laboratory, Kumamoto University. In the system, operated in a ventilation mode, supply fresh Air is dried in a thermal swing honeycomb rotor dehumidifier, and cooled by a regenerative heat exchanger and an evaporative cooler. Return Air is used as a cooling medium in the regenerative heat exchanger, and then heated by hot water in a finned coil heater and discarded through the honeycomb rotor dehumidifier after desorbing the moisture adsorbed from the supply Air stream. The performance of the present cooling system is examined at Regeneration Air temperature as low as 80°C, the amount of enthalpy of about 16.5 kJ/kg can be reduced from the room with the COP (thermal coefficient of performance) of 61% at the superficial Air velocity of 1 m/s. Changes in state of Air during processing are discussed in terms of a psychrometric diagram.
Mohamed Abdelgaied - One of the best experts on this subject based on the ideXlab platform.
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Performance improvement of desiccant Air conditioner coupled with humidification-dehumidification desalination unit using solar reheating of Regeneration Air
Energy Conversion and Management, 2019Co-Authors: Mohamed Abdelgaied, Abd Elnaby Kabeel, Yehya ZakariaAbstract:Abstract The present experimental study aims to enhance a performance of hybrid system of desiccant Air conditioner coupled humidification-dehumidification desalination unit using solar reheating technology. To investigate this idea, the Regeneration Air leaving from desiccant Air conditioner was reheated using the solar energy before entering the humidifier of desalination unit. The solar reheating technology aims to increase the ability of the Regeneration Air to carry the water vapor inside the humidifier and thus increase the freshwater productivity of humidification-dehumidification desalination unit. To obtain the effect of solar reheating technology on the performance of hybrid system, two configurations of the present hybrid system was designed, formed and tested under the weather conditions of Egypt. The first configuration is the desiccant Air conditioner coupled with humidification-dehumidification desalination unit; the second configuration is the desiccant Air conditioner coupled with humidification-dehumidification desalination unit with solar-reheating technology. The experimental results show that; (i) the coefficient of performance of the Air conditioner varying between 0.48–1.11, 0.33–0.61, 0.23–0.42, and 0.18–0.31, for the rate of Regeneration Air 60, 120, 180, and 240 m3/h, respectively; (ii) the enhancement in accumulated freshwater production for using solar reheating technology in the second configuration reached 26.5, 38.96, 13.16, and 11.31%, as compared to the first configuration for the rate of Regeneration Air 60, 120, 180, and 240 m3/h, respectively; (iii) the improvement in gain output ratio for using solar reheating technology in the second configuration reached 42.5, 50.35, 22.1, and 18.85%, as compared to the first configuration for the rate of Regeneration Air 60, 120, 180, and 240 m3/h, respectively.
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Solar energy assisted desiccant Air conditioning system with PCM as a thermal storage medium
Renewable Energy, 2018Co-Authors: Abd Elnaby Kabeel, Mohamed AbdelgaiedAbstract:Abstract The effects of solar energy and Phase Change Material (PCM) on the energy saving of a desiccant Air conditioner have been numerically investigated. Three configurations of desiccant Air conditioner (Type A, Type B, and Type C) are investigated at the same ambient conditions to get beater configurations for the energy-saving potential. The difference between the three configurations represents the source of thermal energy used for heating the Regeneration Air used for reactivation the desiccant material. For Type A the electrical Air heater represents the thermal energy source for heating the Regeneration Air. For Type B the solar energy and electric Air heater represent a source of thermal energy for heating the Regeneration Air. For Type C the solar energy, PCM, and electric Air heater represent a source of thermal energy for heating the Regeneration Air. The numerical results of these simulations are validated by published experimental data, which resulted great agreement between numerical results and experimental data. Also, the economic analysis has been studied to get the beater configurations. The results show that, the average percentage savings in the electrical energy which consumed about 20.85% for Type B and 75.82% for Type C as compared to the Type A.
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Performance improvement of a solar assisted desiccant Air conditioning coupled with condenser for water production
2018 9th International Renewable Energy Congress (IREC), 2018Co-Authors: A. E. Kabeel, Mohamed Abdelgaied, Yehya Zakaria, Ravishankar SathyamurthAbstract:In the present paper, the performances of a solar desiccant Air conditioning system coupled with the condenser for distillate water production are numerically investigated. The aim of the present study condensed the water vapor from the Regeneration Air out from a solar desiccant Air conditioning by feeding it to the condenser to production the distillate water. Production the distillate water, Air conditioning, and energy saving represent the objective of this study. The results show that (i) as process Air discharge increases from 150-450 m3/h, supply Air temperature increases from 18.5-21.6 °C, distillate production decreases from 1.635-0.105 l/h, cooling COP increases from 0.406-0.724, and overall COP decreases from 0.918-0.873 (ii) as the Regeneration Air discharge increases from 75-225 m3/h, supply Air temperature decreases from 21.8-18.4 °C, distillate production increases from 0.009-3.024 l/h, cooling COP decreases from 0.714-0.431, and overall COP increases from 0.718-1.029 (iii) as the Regeneration temperature increases from 75-100 °C, supply Air temperature decreases from 21.2-18.9 °C, distillate production increases from 0.285-1.41 l/h, cooling COP decreases from 0.704-0.555, and overall COP increases from 0.815-0.926.
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Performance evaluation of a solar energy assisted hybrid desiccant Air conditioner integrated with HDH desalination system
Energy Conversion and Management, 2017Co-Authors: Abd Elnaby Kabeel, Mohamed Abdelgaied, Yehya ZakariaAbstract:Abstract In this study, the performances of a solar energy assisted hybrid desiccant Air conditioning system integrated with humidification–dehumidification (HDH) desalination system are numerically investigated. The aim of this study is to benefit from the temperature rise of the Regeneration Air outside of the desiccant conditioning system as well as the water vapor content in this Regeneration Air by feeding it to the humidification-dehumidification water desalination unit to produce distillate water. The distillate water productivity, human thermal comfort issues, and energy saving represent the main objective of the present numerical study. The simulated results developed for subsystems are validated with the published experimental results. The effects of Regeneration Air temperature and flow rate on supply cooled Air temperature, distillate water productivity, the cooling coefficient of performance and overall daily coefficient of performance of the proposed system are investigated. The results show that (i) the distillate water productivity increases from 3.175 to 5.011 L/h and overall daily coefficient of performance decreases from 4.392 to 3.636 with increasing the Regeneration Air temperature from 75 to 95 as (ii) the increase in the Regeneration Air flow rate from 70 to 130 m 3 /h, increases the distillate water productivity from 2.988 to 4.78 L/h and decrease the overall daily coefficient of performance from 4.66 to 3.386. The study demonstrates that the proposed system represents the best options in hot and humid regions.
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A mathematical model for predicting the performance of the solar energy assisted hybrid Air conditioning system, with one-rotor six-stage rotary desiccant cooling system
Energy Conversion and Management, 2013Co-Authors: Ali M. Elzahzby, Abd Elnaby Kabeel, M.m. Bassuoni, Mohamed AbdelgaiedAbstract:Abstract A mathematical model for predicting the performance of solar energy assisted hybrid Air conditioning system (SEAHACS) is presented. The honeycombed silica gel desiccant wheel is used in this study. One-rotor six-stage rotary desiccant cooling system, (two-stage dehumidification process, two-stage pre-cooling process and two-stage Regeneration process) are realized by only one wheel. Three Air streams are involved in the present system. The mathematical model has been validated with the experimental data. The range of Regeneration Air inlet temperature changed from 65 to 140 °C, area ratio of process Air to Regeneration Air change from 1 to 3.57, Regeneration Air inlet velocity from 1.5 to 5.5 m/s have been examined for a range of rotation speed from 6 to 20 rev/h. The optimization of these parameters is conducted based on the moisture removal capacity D , relative moisture removal capacity, dehumidification coefficient of performance and thermal coefficient of performance. At last, the influences of these main parameters on optimal rotation speed are discussed.
Jubair A Shamim - One of the best experts on this subject based on the ideXlab platform.
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theoretical analysis of transient heat and mass transfer during Regeneration in multilayer fixed bed binder free desiccant dehumidifier model validation and parametric study
International Journal of Heat and Mass Transfer, 2019Co-Authors: Jubair A Shamim, Soumyadeep Paul, Kenji Kitaoka, Weilun Hsu, Hirofumi DaigujiAbstract:Abstract A numerical model is presented for the prediction of transient heat and mass transfer characteristics during the Regeneration process in a multilayer fixed-bed, binder-free desiccant dehumidifier. Experiments were carried out in a previous study that provided the benchmark data for validation of the current model under different temperatures and velocities of the Regeneration Air. A spherical microsphere silica gel having a pore diameter of 2.7 nm was used as the adsorbent during the experiments. In the first part of this study, model validation was performed for different temperatures (314.4–325.0 K) and velocities (0.6–0.9 m s−1) of Regeneration Air. The results showed that at a fixed Regeneration temperature (325.0 K), the model predicted mass of the desorbed water as well as the desiccant bed and Air temperatures were in a good agreement with the previously reported experimental results. With a decrease in the temperature and velocity of the Regeneration Air, the model slightly underpredicted the experimentally obtained mass of the desorbed water; however, the deviation remained within a reasonable limit. Upon validation, a parametric study was carried out to show how the heat and mass transfer characteristics of the microsphere silica gel during desorption depended on the intrinsic material properties (e.g., desorption rate constant, diffusivity, and desorption isotherm) and mechanical design parameters of the device (e.g., convective heat transfer coefficient, porosity, and thickness of the desiccant bed).
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experimental evaluation of transient heat and mass transfer during Regeneration in multilayer fixed bed binder free desiccant dehumidifier
International Journal of Heat and Mass Transfer, 2019Co-Authors: Jubair A Shamim, Soumyadeep Paul, Kenji Kitaoka, Weilun Hsu, Hirofumi DaigujiAbstract:Abstract In this study, Regeneration experiments were performed in a previously developed multilayer fixed-bed, binder-free desiccant dehumidifier (MFBDD) in order to investigate the transient heat and mass transfer characteristics during the desorption of condensed water from desiccant material inside the device. A microsphere silica gel (M.S.GEL manufactured by AGC Si-Tech. Co., Ltd., Japan) having a pore diameter of 2.7 nm was used as the desiccant, which was feasible for Regeneration at a temperature slightly above 50 °C. To prevent heat loss during Regeneration, the test section was placed inside a constant-temperature oven. Experiments were performed under several Regeneration conditions to investigate the influence of temperature, humidity, and flow velocity of the Regeneration Air on the heat and mass transfer characteristics of the device. The influence of heat loss from the test section to the surroundings during Regeneration was also determined by precisely controlling the oven temperature. The results revealed that the Regeneration capacity of the device improved with an increase in the Regeneration Air temperature. However, the maximum temperature of Regeneration Air should be optimized for energy-efficient operation of the device according to the Regeneration conditions.
Ruzhu Wang - One of the best experts on this subject based on the ideXlab platform.
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Experimental investigations on desiccant wheels
Applied Thermal Engineering, 2012Co-Authors: Ursula Eicker, Uwe Schürger, Max Köhler, Hui Li, T.s. Ge, Ruzhu WangAbstract:Abstract Experimental investigations on several commercially available and newly fabricated rotors are conducted in two different laboratories to evaluate performance trends. Experimental uncertainties are analysed and the parameters determining the rotor performance are investigated. It is found that the optimal rotation speed is lower for lithium chloride or compound rotors than for silica gel rotors. Higher Regeneration Air temperatures lead to higher dehumidification potentials at almost equal dehumidification efficiencies, but with increasing Regeneration specific heat input and enthalpy changes of the process Air. The influence of the Regeneration Air humidity was also notable and low relative humidities increase the dehumidification potential. Finally, the measurements show that rising water content in the ambient Air causes the dehumidification capacity to rise, while the dehumidification efficiency is not much affected and both specific Regeneration heat input and latent heat change of the process Air decrease. For desiccant cooling applications in humid climates this is a positive trend.
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Experimental investigations on desiccant wheels
Applied Thermal Engineering, 2012Co-Authors: Ursula Eicker, Uwe Schürger, Max Köhler, Hui Li, Yanjun Dai, Tianshu Ge, Ruzhu WangAbstract:Experimental investigations on several commercially available and newly fabricated rotors are conducted in two different laboratories to evaluate performance trends. Experimental uncertainties are analysed and the parameters determining the rotor performance are investigated. It is found that the optimal rotation speed is lower for lithium chloride or compound rotors than for silica gel rotors. Higher Regeneration Air temperatures lead to higher dehumidification potentials at almost equal dehumidification efficiencies, but with increasing Regeneration specific heat input and enthalpy changes of the process Air. The influence of the Regeneration Air humidity was also notable and low relative humidities increase the dehumidification potential. Finally, the measurements show that rising water content in the ambient Air causes the dehumidification capacity to rise, while the dehumidification efficiency is not much affected and both specific Regeneration heat input and latent heat change of the process Air decrease. For desiccant cooling applications in humid climates this is a positive trend. © 2011 Elsevier Ltd. All rights reserved.
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A simulation study of heat and mass transfer in a honeycombed rotary desiccant dehumidifier
Applied Thermal Engineering, 2003Co-Authors: Xinglei Zhang, Ruzhu WangAbstract:A one-dimensional coupled heat and mass transfer model, which is expected for use in designing and manufacturing of a honeycombed rotary desiccant wheel, is presented in this paper. The mathematical model has been validated using a real desiccant wheel, and the calculation results are in reasonable agreement with the experimental data. Based on this model, the temperature and humidity profiles in the wheel during both the dehumidification and the Regeneration processes are analyzed and verified by experimental data. The numerical results indicate that in the Regeneration process a hump curve of Air humidity ratio along the channel exists all the time. In the Regeneration process the hump of Air humidity ratio moves from the duct entrance to the duct exit and increases gradually until the hump reaches the duct exit, where the hump will drop subsequently. The effects of velocity of Regeneration Air Vreg inlet temperature of Regeneration Air Treg and velocity of process Air Vad on the hump moving speed are investigated. To improve the performance of desiccant wheel, it is essential to accelerate the hump moving from the duct entrance to the duct exit as soon as possible.