Airflow Profile Research Articles

Analysis of the effects of package design on the rate and uniformity of cooling of stacked pomegranates: Numerical and experimental studies

Computational fluid dynamics (CFD) model was developed, validated and used to analyse cooling characteristics of two different package designs (CT1 and CT2) used for postharvest handling of pomegranate fruit. The model incorporated geometries of fruits, packaging box, tray and plastic liner. Thin layer of plastic material with conservative interface heat flux was used to model liners. The accuracy of the model to predict airflow and temperature distributions were validated against experimental data. The model predicted airflow through the stacks and cooling rates within experimental error. Stack design markedly affected the airflow profile, rate and uniformity of cooling. The cooling rate of the two package designs differed by 30% and plastic lining increased the average 7/8th cooling times from 4.0 and 2.5h to 9.5 and 8.0h for the CT1 and CT2 stacks, respectively. Profile of high and low temperature regions depended considerably on packaging box design.

Analysis of airflow and heat transfer inside fruit packed refrigerated shipping container: Part I – Model development and validation

This paper developed and validated a computational fluid dynamic (CFD) model of airflow and produce cooling inside a fully loaded refrigerated shipping container (reefer) based on porous medium approach. Wind tunnel tests were used to obtain the pressure drop characteristics of palletized stack of apple fruit. Detailed structure of the T-bar floor of the reefer and resistance to airflow of wooden pallets were included in the model. Airflow and temperature data obtained from a fully loaded, full-scale reefer were used to validate the model. The model successfully reproduced the airflow and temperature profiles inside the reefer, and in addition, high and low cooling regions were identified. At 24 h, the average temperature inside the reefer reached 2.7 °C (exp.) and 2.8 °C (numerical) from an initial 9.5 °C with an overall standard deviation of 1.70 °C (exp.) and 2.32 °C (numerical). Model predictions were acceptably accurate with an average error of 26 and 18% in predicting airflow and temperature, respectively. The absence of vent-hole on the bottom face of the packaging box caused non-uniform airflow and a highly heterogeneous cooling. These demonstrated the importance of packaging design that take into account the airflow path inside reefers.

Optimisation and analysis of a heat pipe assisted low-energy passive cooling system

Passive cooling using windcatchers have been utilised in the past by several Middle East countries to capture wind and provide indoor ventilation and comfort without using energy. Recently, researchers have attempted to improve the cooling performance of windcatchers by incorporating heat pipes. The present work encompasses existing research by optimising the arrangement of heat pipes in natural ventilation airstreams using numerical and experimental tools. The airflow and temperature profiles were numerically predicted using Computational Fluid Dynamics (CFD), the findings of which were quantitatively validated using wind tunnel experimentation. Using a source temperature of 314K or 41°C and an inlet velocity of 2.3m/s, the streamwise distance-to-pipe diameter ratio was varied from 1.0 to 2.0 and the emergent cooling capacities were established to comprehend the optimum arrangement. The results of this investigation indicated that the heat pipes operate at their maximum efficiency when the streamwise distance is identical to the diameter of the pipe as this formation allows the incoming airstream to achieve the maximum contact time with the surface of the pipes. In addition, the findings showed that any increase in streamwise spacing leads to the formation of a second bell curve representing an increase in air velocity which simultaneously reduces the contact time between the airstream and the heat pipes, decreasing its effectiveness. The study quantified that the optimum streamwise distance was 20mm at which the Sd/D (streamwise distance-to-pipe diameter) ratio was 1.0. The thermal cooling capacity was subsequently found to decrease by 10.7% from 768W to 686W when the streamwise distance was increased to 40mm (Sd/D ratio of 2.0). The technology presented here is subject to an international patent application (PCT/GB2014/052263).

Temperature Regulations of Pseudo Noise Generator Based Optical Transmitter Using Airflow and Heat Sink Profile

For any electronic device, junction temperature is the final temperature after that device became dead. In this paper the temperature of PN based optical transmitter is regulated using heat sink and airflow. Target device is operated at different operating frequencies for LVCMOS IO standard (LVCMOS12, LVCMOS15, LVCMOS18 and LVCMOS25) with two airflow values (250 MFL and 500MFL) and Heat sink values (Low profile, Medium profile and high profile). There is overall 20% reduction at 1000GHz the reduction for LVCMOS12 and for LVCMOS25 71% reduction is recorded for junction temperature. At all frequencies the heat sink profile and airflow significantly reduces the junction temperatures for target devices using LVCMOS25 IO standard. This design makes the target device, energy efficient. Finally this system will be integrated with other optical components to make optical communication system green. Xilinx ISE14.7.1.2 design tool is used to perform the experiment

Indoor mould growth prediction using coupled computational fluid dynamics and mould growth model

This study investigates, using in-situ and numerical simulation experiments, airflow and hygrothermal distribution in a mechanically ventilated academic research facility with known cases of microbial proliferations. Microclimate parameters were obtained from in-situ experiments and used as boundary conditions and validation of the numerical experiments with a commercial computational fluid dynamics (CFD) analysis tool using the standard k–e model. Good agreements were obtained with less than 10% deviations between the measured and simulated results. Subsequent upon successful validation, the model was used to investigate hygrothermal and airflow profile within the shelves holding stored components in the facility. The predicted in-shelf hygrothermal profile was superimposed on mould growth limiting curve earlier documented in the literature. Results revealed the growth of xerophilic species in most parts of the shelves. The mould growth prediction was found in correlation with the microbial investigation in the case-studied room reported by the authors elsewhere. Satisfactory prediction of mould growth in the room successfully proved that the CFD simulation can be used to investigate the conditions that lead to microbial growth in the indoor environment.

Novel approach to analytical modelling of steady-state heat transfer from the exterior of TEFC induction motors

The purpose of this paper is to propose a novel approach to analytical modelling of steady-state heat transfer from the exterior of totally enclosed fan-cooled induction motors. The proposed approach is based on the geometry simplification methods, energy balance equation, modified correlations for forced convection, the Stefan-Boltzmann law, air-flow velocity profiles, and turbulence factor models. To apply modified correlations for forced convection, the motor exterior is presented with surfaces of elementary 3-D shapes as well as the air-flow velocity profiles and turbulence factor models are introduced. The existing correlations for forced convection from a short horizontal cylinder and correlations for heat transfer from straight fins (as well as inter-fin surfaces) in axial air-flows are modified by introducing the Prandtl number to the appropriate power. The correlations for forced convection from straight fins and inter-fin surfaces are derived from the existing ones for combined heat transfer (due to forced convection and radiation) by using the forced-convection correlations for a single flat plate. Employing the proposed analytical approach, satisfactory agreement is obtained with experimental data from other studies.

Development of Wind Tunnel for Ultrafine Palm Oil Fuel Ash Separator

Palm Oil Fuel Ash (POFA) is a pozzolanic material that has great potential in concrete production. POFA sizes range from 1 to 10 μm is preferable. Thus, there is a need for efficient method to separate the POFA according to the sizes needed. This study explores the idea of using a simple wind tunnel as a separator for ultrafine POFA. The existing operation of the wind tunnel is simulated using ANSYS-CFX, a numerical modelling software. The identified weakness of the wind tunnel design is located at the hopper. The wind tunnel is simulated with a different air inlet velocity in order to visualize the air flow profile as well as air flow energy at the hopper. Different air inlet velocities has a similar air flow profile but the air flow intensity is different. For further study the modifications of the air flow profile were conducted. By altering the hopper angle shows that the air flow profile is changed. Based on the simulation results, the hopper at 60° yields the best flow characteristic. At angle 60° of the hopper, the air flow is mostly directed downward into the tunnel and the air flow energy is low. Therefore, it allows the POFA to be directed into the tunnel and reduced the ultrafine POFA losses at the tip of the hopper. This practical method utilizes a simple open wind tunnel that enables the process to be more efficient and cost efficient thus the production of ultrafine POFA can be increased.

Simulation of dry powder inhalers: Combining micro‐scale, meso‐scale and macro‐scale modeling

The flow of carrier particles, coated with active drug particles, is studied in a prototype dry powder inhaler. A novel, multiscale approach consisting of a discrete element model (DEM) to describe the particles coupled with a dynamic large eddy simulation (LES) model to describe the dynamic nature of the flow is applied. The model consists of three different scales: the micro‐scale, the meso‐scale, and the macro‐scale. At the micro‐scale, the interactions of the small active drug particles with larger carrier particles, with the wall, with the air flow, and with each other is thoroughly studied using discrete element modeling and detailed computational fluid dynamics (CFD), i.e., resolving the flow structures around the particles. This has led to the development of coarse‐grained models, describing the interaction of the small active drug particles at the larger scales. At the meso‐scale the larger carrier particles, and all of their interactions are modeled individually using DEM and CFD‐LES. Collisions are modeled using a visco‐elastic model to describe the local deformation at each point of particle‐particle contact in conjunction with a model to account for cohesion. At the macro‐scale, simulations of a complete prototype inhaler are carried out. By combining the relevant information of each of the scales, simulations of the inhalation of one dose from a prototype inhaler using a patient relevant air flow profile show that fines leave the inhaler faster than the carrier particles. The results also show that collisions are not important for particle‐particle momentum exchange initially but become more important as the particles accelerate. It is shown that for the studied prototype inhaler the total release efficiency of the fine particles is between 10 and 30%, depending on the Hamaker constant, using typical settings for the properties of both particles. The results are also used to study regions of recirculation, where carrier particles can become trapped, and regions where fines adhere to the wall of the device. © 2016 American Institute of Chemical Engineers AIChE J, 63: 501–516, 2017

A computational analysis of nasal vestibule morphologic variabilities on nasal function

Although advances in computational modeling have led to increased understanding of nasal airflow, not much is known about the effects of normal sinonasal anatomic variabilities on nasal function. In this study, three distinct variations in the human nasal vestibule airspace that have not been previously described were identified. Computational fluid dynamics modeling of nasal airflow profile in each identified variation of nasal vestibule phenotype was conducted to assess the role of these phenotypes on nasal physiology. Three-dimensional reconstructions of the nasal geometry in sixteen subjects with normal radiographic sinonasal images were created and each respective unilateral nasal cavity was classified as Notched, Standard, or Elongated phenotype based nasal vestibule morphology. Steady state, laminar and incompressible flow simulations were performed in the nasal geometries under physiological, pressure-driven conditions with constant inspiratory pressure. Results showed that at localized regions of the unilateral nasal cavity, average resistance was significantly different among nasal vestibule phenotypes. However, global comparison from nostril to choana showed that average resistance was not significantly different across phenotypes; suggesting that with normal anatomic variations, the nose has a natural compensatory mechanism that modulates localized airflow in order to achieve a desired amount of global airflow.

Effect of Air to Air Fixed Plate Enthalpy Energy Recovery Heat Exchanger Flow Profile on Air Conditioning System Energy Recovery

Fixed plate enthalpy heat exchanger which utilizes permeable material as heat and moisture transfer surface has been used as an energy recovery system to recover sensible and latent heat in HVAC systems. The heat exchanger effectiveness is affected by the air flow profile. It is well known that counter flow configuration provides highest effectiveness, however, in real applications, it is not possible to implement a counter flow configuration, as both inlet and outlet ducts of the two flow streams are located on the same side of the heat exchanger. Therefore, several quasi-counter-flow heat exchanger designs including Z-shaped, L-shaped, Z-shaped opposite flow configurations are proposed in this research and their effect on energy consumed by an air conditioning cooling coil has been investigated, where each of the proposed heat exchanger is incorporated in an air conditioning cooling coil model. The modeled cooling coil energy consumption and energy recovered by the heat exchangers are evaluated under Kuala Lumpur weather conditions. It has been found that an air conditioner coupled with L-shaped heat exchanger recorded up to 20% increase in energy recovery in comparison with Z-shaped oposite and Z-shaped heat exchanger.

Characterizing Airflow Profile in the Postoperative Maxillary Sinus by Using Computational Fluid Dynamics Modeling: A Pilot Study

Maxillary antrostomy is commonly performed during endoscopic sinus surgery. Little is known about the association surrounding recalcitrant maxillary sinusitis, antrostomy size, and intranasal airflow changes. Furthermore, the interaction between sinus mucosa and airflow is poorly understood. This study used computational fluid dynamics (CFD) modeling to investigate postoperative airflow characteristics between diseased and nondiseased maxillary sinuses in subjects with recurrent disease. A retrospective review of patients from a tertiary-level academic rhinology practice was performed. Seven subjects with endoscopic evidence of postoperative maxillary sinus disease that presented as chronic unilateral crusting at least 1 year after bilateral maxillary antrostomies were selected. A three-dimensional model of each subject's sinonasal cavity was created from postoperative computed tomographies and used for CFD analysis. Although the variables investigated between diseased and nondiseased sides were not statistically significant, the diseased side in six subjects had a smaller antrostomy, and five of these subjects had both reduced nasal unilateral airflow and increased unilateral nasal resistance on the diseased side. The ratio of posterior wall shear stress (WSS) of the maxillary sinus to the total WSS was higher on the diseased side in six subjects. Results also showed strong correlations between antrostomy and CFD variables on the diseased side than on the nondiseased side. This pilot study showed that the majority of the simulated sinonasal models exhibited common characteristics on the side with persistent disease, such as smaller antrostomy, reduced nasal airflow, increased nasal resistance, and increased posterior WSS. Although statistical significance was not established, this study provided preliminary insight into variables to consider in a larger cohort study.

Investigation on the nasal airflow characteristics of anterior nasal cavity stenosis.

We used a computational fluid dynamics (CFD) model to study the inspiratory airflow profiles of patients with anterior nasal cavity stenosis who underwent curative surgery, by comparing pre- and postoperative airflow characteristics. Twenty patients with severe anterior nasal cavity stenosis, including one case of bilateral stenosis, underwent computed tomography (CT) scans for CFD modelling. The pre- and postoperative airflow characteristics of the nasal cavity were simulated and analyzed. The narrowest area of the nasal cavity in all 20 patients was located within the nasal valve area, and the mean cross-sectional area increased from 0.39 cm2 preoperative to 0.78 cm2 postoperative (P<0.01). Meanwhile, the mean airflow velocity in the nasal valve area decreased from 6.19 m/s to 2.88 m/s (P<0.01). Surgical restoration of the nasal symmetry in the bilateral nasal cavity reduced nasal resistance in the narrow sides from 0.24 Pa.s/mL to 0.11 Pa.s/mL (P<0.01). Numerical simulation of the nasal cavity in patients with anterior nasal cavity stenosis revealed structural changes and the resultant patterns of nasal airflow. Surgery achieved balanced bilateral nasal ventilation and decreased nasal resistance in the narrow region of the nasal cavity. The correction of nasal valve stenosis is not only indispensable for reducing nasal resistance, but also the key to obtain satisfactory curative effect.

A study on optimising heat pipe geometrical parameters for sustainable passive cooling within the built environment

The way in which heat pipes are arranged plays an important role on the overall effectiveness of this sustainable thermal system. A numerical and experimental analysis into determining the optimum heat pipe streamwise distance for providing passive airside cooling in ventilation airstreams was carried out. The airflow and temperature profiles were numerically predicted using Computational Fluid Dynamics (CFD), the findings of which were quantitatively validated using wind tunnel experimentation. Using the heat pipe diameter (D) of 20 mm, the spanwise thicknesses were varied from 44 mm (St/D ratio of 2.2) to 52 mm (St/D ratio of 2.6). In order to ensure sustainable operation of the system, water was used as the heat pipe working fluid. Keeping the boundary conditions constant for all modes (inlet velocity of 2.3 m/s and inlet temperature of 314K), the rate of heat transfer was found to be directly proportional to the temperature difference between inlet and outlet interface. The findings determined that the spanwise thickness of 50 mm (St/D ratio of 2.5) provided the highest heat transfer in comparison to the other analysed models at 768 W. The overall effectiveness of the system was found to decrease from 5.6% to 4.7% when the spanwise thickness reduced from 50 mm to 44 mm. A good agreement was obtained between the numerical and experimental findings with a maximum error of 1.6% for temperature and 14.6% for velocity parameters. The investigation successfully evaluated the performance of heat pipes under varying geometrical arrangement, when utilised for the purpose of pre-cooling ventilation airstreams for a sustainable built environment.

Experimental investigation of the effects of airflow nonuniformity on performance of a fin-and-tube heat exchanger

The effects of airflow nonuniformity on the thermal–hydraulic performance of a fin-and-tube heat exchanger were investigated experimentally. The test subject was a four-depth-row fin-and-tube heat exchanger with face split tube circuitry. Nonuniform inlet air distribution was generated by partially blocking the heat exchanger entrance cross-section. It was found that airflow nonuniformity causes thermal effectiveness deterioration and pressure drop increase. The size of effectiveness deterioration and pressure drop increase depend on the degree of airflow nonuniformity as well as on the orientation between airflow nonuniformity and tube-side fluid circuitry. For most of the observed nonuniform airflow profiles, which had low or moderate degrees of airflow nonuniformity, the effectiveness deterioration was between 5% and 10%, while the pressure drop increase was between 10% and 20%. For severely nonuniform airflow profiles the effectiveness deterioration was up to 30% and the pressure drop increase was up to 90%.

CTHS Based Energy Efficient Thermal Aware Image ALU Design on FPGA

Image ALU is a special type of ALU exclusively designed to perform arithmetic and logical operation on Image only. This Image ALU design is able to perform 14 operations. In this work, we have proposed a novel 4-stages energy efficient CTHS (C-Capacitance Scaling, T-Thermal Scaling, H-HSTL I/O Standard, S-SSTL I/O Standard) approach for Low Power and Thermal Aware Image ALU Design. CTHS technique is achieving 81.79 % reduction in power consumption which is more than the power reduction by method discussed in Shrivastava et al. (IEEE Trans Very Large Scale Integr Syst 18(6):988---997, 2010); Yoonjin and Mahapatra (IEEE Trans Very Large Scale Integr Syst 18(1):15---28, 2010); Chatterjee and Sachdev (IEEE Trans Very Large Scale Integr Syst 13(11):1296---1304, 2005); Wijeratne et al. (IEEE J Solid State Circuits 42(1):26---37, 2007); Nehru et al. (International conference on advances in engineering, science and management pp 145---149, 2012); Ho et al. (IEEE international symposium on circuits and systems pp 353---356, 2013); Rani et al. (3rd in international conference on electronics computer technology pp 224---228, 2011) for ALU. There is 38.63 % reduction in I/O Power and 46.42 % reduction in leakage power, when we scale down capacitance from 50 to 5 pF on 28 nm technology based Kintex-7 FPGA on 100 GHz device operating frequency. FPGA is a Filed Programmable Gate Array. There is 67.05 % reduction in I/O Power when we scale down ambient temperature from 50 to 10 °C on 100 GHz frequency. There are 5 different climates in koppen climate classification. We are taking 5 different values in order to nearly represent 5 climates. Using high profile Heat Sink and 500 LFM Airflow, there is 75.39 % leakage power reduction from the last optimized result of capacitance scaling and 85.84 % leakage power reduction from the initial power dissipation. On 3rd stage, using HSTL I/O Standard, there is 64.53 % power reduction from the initial power dissipation. There is 41.06, 59.26, 78.75 % power reduction from HSTL_II_DCI_18 to HSTL_I_12 on 100, 10 and 1 GHz. On 4th and final stage, using SSTL I/O Standard, there is 81.79 % power reduction from the initial power dissipation. There is 61.83 % reduction in junction temperature, when we apply 500 LFM airflow and high profile heat sink in compare to 250 LFM airflow and no heat sink. LFM is an acronym for Linear Feet per Minute. LFM is a unit of airflow that help us to control junction temperature of FPGA. Unit of leakage power is Watt (W) and Junction Temperature is degree Celsius (°C).

A high-linearity DC planar Ionic anemometer

A high-linearity DC planar ionic anemometer which can measure the airflow velocity of boundary-layers near a surface was constructed and tested. The differential anemometer described in this paper includes two symmetrical cathodes and one anode with a sharp tip. High voltage is applied to the anode to generate a symmetrical ionic discharge, and then the airflow deflects the symmetrical ion distribution and produces a differential current between the two cathodes. It can detect bidirectional airflow velocity and is more crash-resistant than traditional hot-wire anemometers. It has minimum impact on the airflow profile because of its thin-shape design and achieves high measurement accuracy. A series of tests have been done for the static characteristics and dynamic performance by changing structural parameters such as cavity depth, gap width, anode tip angle, cathode width and length. The results show that the cavity depth is the most important structural parameter since it has the greatest effect on the stability of the gas discharge, which is affected by ion mobility and friction between ions and the bottom of cavity. The gap width plays a decisive role in the current and sensitivity values. Besides, the uncertainties of the tests have been analyzed by introducing the error bars and the testing errors are in reasonable ranges. The anemometer is cost-effective and offers the possibility of building a MEMS version in the future.

Open Volumetric Air Receiver Based Solar Convective Aluminum Heat Treatment Furnace System

Abstract The current heat treatment processes make use of electricity or fuel for generating heat. Solar energy is available in abundance in the states of Rajasthan and Gujarat in India. Annual global solar radiation of about ≥2400 kWh/m2 is received in these regions. Use of the abundant solar thermal energy in heat treatment of metals would saveenergy and fuels. In view of this a concept of solar convective furnace system is described in this paper. As a starting point, heat treatment of aluminium is considered. For this system, requirements of industrial furnace are taken as basis.A scale-down retrofitted furnace is designed and analysed.The importance of different process stages like, solar thermal energy absorption, storage and utilization in design of such a system is presented.A thermodynamic analysis is performed to derive requirements for the achievement of a uniform heating at a pre-determined rate. Control strategy to meet the requirements is worked out. Air flow profile in the furnace is analyzed using CFD as a tool. Laser Doppler Velocimetery technique is used for measurement of velocity in a Plexiglas model of the scale-down furnace. Flow analysis using theadopted CFD tool shows non uniformities in air flow profile. To counter this, further modifications and improvements in the furnace structure are suggested. Evaluation of Open Volumetric Air Receiver (OVAR) using installed solar air tower simulation facility is also presented in the paper.

Passage of Charged Particles Through Segmented Axial-Field Tubes

We propose a mathematical theory explaining the passage of charged aerosol particles through segmented tube mobility filters recently suggested by Bezantakos et al. A segmented tube is composed of conductive segments and semiinsulating segments, which are made of electrostatic dissipative material. Electric potential applied to a semi-insulating segment generates a uniform electric field and holds back penetration of charged particles. Analytic equations of penetration efficiency of nondiffusing particles are derived for problems, where the length of the decelerating semi-insulating section exceeds the tube diameter at least twice and the air flow profile is uniform or follows the Hagen–Poiseuille law. The equations well explain the experimental results obtained by Bezantakos et al. The requirements for the tube parameters necessary for the application of analytic equations are derived by means of a numerical model. The motion of particles in segmented tube mobility filters is illustrated with diagrams co...

Temperature Control of Pseudo Noise Generator Based Optical Transmitter using Airflow and Heat Sink Profile at High Speed Transceiver Logic IO Standard

Junction temperature is the final temperature of any device, after that device became dead. In this paper, junction temperature of target device i.e. Pseudo Noise sequence random generator based optical transmitter is controlled using heat sink profile and airflow. Heat sink and airflow are the cooling techniques for thermal efficient design on FPGA. We operated target device at high speed transceiver logic (HSTL) on FPGA at 1, 10,100 and 1000 (GHz) operating frequency. Each IO standard is examined with two airflow values (250 MFL and 500MFL) and Heat sink values (Low profile, Medium profile and high profile). For HSTL_I the reduction in junction temperature is (4%, 5%, 16% and 20%), HSTL_III (2%, 4%, 40%, and 67%), HSTL_I_18 (2%, 15%, 59%, and 68%), HSTL_III_18 (2.4%, 19%, 62%, and 74%) is recorded at respective frequencies. Significant reduction of 74% in junction temperature is observed at 1000GHz using HSTL_III_18. We conclude that for frequencies above 10GHz the heat sink profile and air flow significantly reduces the junction temperature using HSTL_III_18. This design makes the target device, energy efficient, system will be integrated with other optical components to make optical communication system green. Xilinx ISE14.7.1.2 design tool is used to perform the experiment.

The Effect of Added Dead Space on Optimal Neuro-Muscular Drive and Respiratory Signals under Hypercapnia

The problem concerning the nature and the function of the dead space is of basic importance for the fullcomprehension of the respiratory physiology and pathophysiology. To study the effect of an imposed external deadspace on the optimal respiratory control system, we simulated the optimal neuro-muscular drive and respiratorysignals, including instantaneous airflow and lung volume profiles, with dead space loading under hypercapnia. Thedead space measurement model by Gray was employed and the human respiratory control simulator based on anoptimality hypothesis was implemented. The ventilatory control simulations were performed with external dead spaceloading of 0, 0.4 and 0.8 liters under rest condition (PICO2=0%) and CO2 inhalation of 3% to 7%. The optimization ofthe respiratory signals and model behavior of the optimal respiratory control under dead space loading andhypercapnia were verified and found to be in general agreement with experimental findings.