Optimum Air Velocity Research Articles

Drying characteristics of horse mackerel ( Trachurus japonicus) dried in a heat pump dehumidifier

In this study, a heat pump dehumidifier (HPD) was designed and constructed to investigate the drying characteristics of horse mackerel experimentally. Effects of surface load, drying air temperature, sodium chloride (NaCl) content in the osmotic solution, tempering, evaporator bypass air ratio (BAR) and air velocity on the drying characteristics of horse mackerel have been investigated. Experimental results showed that a high surface load of 8 kg/m 2 resulted in lower drying rate (DR), and surface load of 6 kg/m 2 was preferred by considering specific moisture evaporation rate (SMER) and total colour difference (Δ E). DR increased with increase in the drying air temperature. In view of SMER and Δ E, temperature at 20–30 °C was optimum air temperature for drying horse mackerel by HPD. However, NaCl content in the osmotic solution and tempering played a minor role during drying horse mackerel by HPD. BAR of 0.6–0.8 obtained the maximal SMER. The optimum air velocity for drying horse mackerel by HPD was 2.0–3.0 m/s. Furthermore, HPD provided an alternative way to process intermediate moisture fillets.

Sensible heat loss: the broiler's paradox

Recent decades have seen significant progress in the genetic selection of fast-growing meat-type broiler chickens. However, fast growth has coincided with inferior development of the visceral systems, especially the cardiovascular organs, contributing to difficulties in coping with heat stress. Global mean surface temperatures are expected to rise during the coming years and climate control systems are expensive. This situation, where growth rate and heat production increases on a yearly basis and the future foresees increasing temperatures, demands an efficient means to economically improve the acquisition of thermotolerance by broiler chickens in hot climates. In homeotherms, three direct responses participate in thermotolerance acquisition: rapid thermal shock response, acclimation and epigenetic adaptation. Together with physiological understanding, it is important to understand the physical aspects of broiler excess heat dissipation. This paper focuses on air velocity as a principal parameter which dramatically affects sensible heat loss and its contribution to the ability of acclimated or epigenetic adapted broilers to efficiently maintain a favourable energy balance under hot conditions. Heat transfer equations and models for different body parts are presented which were used to determine energy balance components at different air speeds based on thermal imaging. The studies reviewed demonstrate that: (a). air velocity plays a major role in energy balance at high ambient temperatures; (b). the optimal air velocity for achieving maximal growth performance differs at different ambient temperature and has a point of inflection at ambient temperature below 30°C, where chilling affects the broiler;(c). high air velocity at high ambient temperatures affects the ability of broilers to maintain total body water, most probably as a result of cutaneous water loss; (d). thermal conditioning at an early age increases the capacity of broilers to efficiently lose heat by radiation and convection; (e). genetic selection for growth performance has been to some extent at the expense of the broiler's ability to maintain favourable energy and water balances.

대류난방시 실내열환경에 관한 연구 - 온도 및 기류속도에 대한 온열쾌적감-

Draft is defined as an unwanted local cooling of the human body caused by air movement. It is a serious problem in many ventilated or air conditioned buildings. Often draft complaints occur although measured velocities in the occupied zone maybe lower than prescribed in existing standards. Purpose of this study is to clarify the evaluation of thermal comfort based on temperature and air velocity in winter. Experiments were performed in an environmental chamber in winter. Indoor temperature and air velocity was artificially controlled. The experiments were performed to evaluate temperature conditions and air velocity conditions by physiological and psychological responses of human. According to physiological responses and psychological responses, it was clear that the optimum air velocity is about 0.15 m/s and 0.30 m/s.

Effect of air velocity on fresh Japanese noodle (Udon) drying

The effect of air velocity on the drying kinetics of Japanese noodle (udon) was investigated. The drying of fresh udon was carried out under six air velocities of 0.50, 0.75, 1.00, 1.25, 1.88, and 3.00 m/s at a constant temperature (40°C) and relative humidity (70%). The drying rate increased with air velocity. The apparent moisture diffusivities were determined using a diffusion model taking internal and external mass transfer resistances into account. The effect of air velocity on the apparent moisture diffusivity was found to have no influence on the drying rate for air velocity above 2 m/s in the initial drying stage, 1 m/s in the main drying stage, respectively. The effect of air velocity on udon drying has been determined, hence allowing optimal air velocity estimation from the economic point of view.

Air Velocity Alters Broiler Performance Under Harsh Environmental Conditions

The effect of air velocity (AV) on weight gain, feed intake, and feed efficiency was studied in male broiler chickens exposed to a constant 35 C, 60% RH, and continuous illumination from 4 through 7 wk of age. In two separate trials, AV of 0.5, 1.5, 2.0, and 3.0 m/s (Trial 1) and 1.0, 1.5, 2.0, and 2.5 m/s (Trial 2) were used. The fifth week was used for acclimation to the targeted environmental conditions. Weight gain was significantly higher in broilers exposed to AV of 1.5 and 2.0 m/s in both trials, which coincided with significantly higher feed intake and feed efficiency. Exposure to the low AV (0.5 and 1.0 m/s) resulted in weight gain, feed intake, and feed efficiency that were less than those of broilers exposed to high AV (2.5 and 3.0 m/s). In all treatments, broilers developed hyperthermia, but there were no significant differences in body temperature (Tb) among the birds. It can be concluded that AV has a significant effect on broiler performance; the optimal AV was found to be 1.5 to 2.0 m/s.

Pneumatic Transport of Solids Using Dry Air

Abstract Air drilling is defined as the process of making boreholes by utilizing air or gas as the circulating fluid. Studies of the hydrodynamics associated with the air drilling process have been ongoing at Penn State since 1985. In this study, dry air was utilized as the circulating medium. Field and laboratory tests have indicated that coincidental to expansion of air across bit-nozzles is the formation of water droplets which accumulate in the wellbore and along the walls of the drill-pipe and hole. The presence of this free-water can become a source of error in studies of the pneumatic transport of solids. In this study, humidity and air density were measured and incorporated into the results. The use of Ottawa sand for laboratory investigations of pneumatic transport can yield erroneous results because of the size attrition realized in circulating the sand. To eliminate the problem with particle attrition, the experiments were conducted with sintered bauxite spheres. The experiments indicated that "choking" occurred at low annular velocities where gravitational effects on the particles predominated and large pressure drops were observed. As the annular air velocities were increased, a minimum pressure drop was observed. This minimum pressure drop occurred at the optimum air velocity where air drilling is optimized. As the air velocities were further increased, the pressure drops increased as the frictional effects predominated. Further, it was observed that in these experiments, optimum air velocity depended primarily on particle size. Minimum pressure drops also depends on particle size and on solids mass flow rate. Optimum air velocities and minimum annulus pressure drops increased when larger particle sizes were utilized. Introduction In the United States and Canada, air drilling has been used extensively for the drilling of oil and gas wells. The use of this technique has resulted in significant savings in both well costs and rig time. These cost savings have resulted in the development of reservoirs that would otherwise not be developed using conventional mud drilling systems. Perhaps the greatest advantage of air drilling, when compared to drilling with mud, is the increased rate of penetration(1–3). Other advantages to air drilling include longer bit life, minimization of damage to the wellbore, and elimination of some of the problems commonly associated with mud drilling such as lost circulation(4–8). With the many advantages cited for the use of air or gas it remains an under used technology. It has been estimated that air drilling could be used in more than 30% of all land wells drilled in the United States(9). Presently, the actual figure is estimated to be about 10%. The primary reason that air drilling has not gained widespread acceptance and usage in the oil and gas industry is the lack of a scientifically-based engineering method for drill design(10). Current air drilling design methods are based on empiricism and consist primarily of rules-of-thumb. Procedures such as Angel's method and its derivatives are too simplistic because they assume a single phase friction factor for a two-phase system.

Design of a circular slot hood for a local exhaust system and its application to a mixing process for fine particles and organic solvents.

The characteristics of airflow (pressure loss and entry loss factor) were measured around a circular slot hood for its application to a local exhaust system. Centerline velocity, defined as the ratio of air velocity on the centerline of the slot hood to average slot face velocity, was found to be independent of the airflow rate. The relationship between the centerline velocity and the ratio of centerline distance to slot width was also found to be independent of the slot size. The empirical centerline velocity equation for the circular slot hood was thus constructed to design the local exhaust system. Recommended values for airflow rate into the circular slot hood and the average slot face velocity were found to be 20.14 m3/min and 8.55 m/sec, respectively. The optimum air velocity at a capture point was also found to be 5% of the average slot face velocity, i.e. 0.43 m/sec, and the effective ventilation with the hood was achieved with these values. The local exhaust system with the circular slot hood was installed for a mixing process of fine particles and organic solvents in a magnetic coating works. The effectiveness of the circular slot hood was confirmed by measuring the concentrations of airborne particles and vapors before and during the operation of the local exhaust system.

An Experimental Study of Particle Transport In a Deviated Wellbore

Abstract Air-drilling is defined as the process of making bore-holes by utilizing air or gas as the circulating fluid. Penn State has been systematically studying the fluid dynamics associated with air-drilling in vertical wells since 1985. Recently this work was expanded to include an investigation of the effects of wellbore angle on key air-drilling design parameters such as annular air velocity and minimum pressure drop. This paper is a preliminary report of the findings of this investigation. An improved understanding of the effects of annular deviations on the pneumatic transport of cuttings will help to develop new design criteria for drilling deviated wells using air as the circulating medium. An experimental wellbore apparatus was constructed to simulate air-drilling in a deviated wellbore. The apparatus was designed to permit variations ill the volumetric air flow rate delivered via the drill pipe. Changes in penetration rate were simulated by controlling the mass flow rate of the sand particles into the annulus. The model also provided for the visual observation of multiphase flow and the measurement of pressure losses in the annulus space. The data obtained from experiments conducted vertically were compared to air velocities determined using Angel's model. Significant differences are noted because Angel's model ignores the variation in particle sizes and particle size distribution, and only predicts the minimum air flow rate necessary to clean the wellbore. The effects of wellbore deviation were examined and analysed. For a given particle size, the effects of even small deviations from vertical were apparent. The analysis further indicated that both the minimum pressure drop and the optimal annular air velocity are strongly dependent on the angle of the annulus. Using this information, empirical equations were developed to predict minimum pressure drop and optimum annular air velocity. These equations are based upon data which can be collected in the field and consequently they may prove helpful in improving air drilling operations in the field. Introduction Air-drilling is defined as the process of making bore-holes by utilizing air or gas as the circulating fluid. The advantages of air-drilling over conventional mud-drilling have been well documented (11 –5). Drilling muds are expensive to make and maintain. Moreover, disposal of drilling muds in an environmentally prudent fashion can also be expensive. Air by comparison, is readily available. cost-free, and environmentally benign. Moreover, the use of air as the circulating fluid can result in much higher rates of penetration and higher footage runs per bit. The other noteworthy benefits realized in its correct utilization include better formation parameter estimation, minimized formation damage, minimized well bore damage, and mitigation of lost circulation problems in certain drilling environments. Where feasible, it makes economic sense to use air. Air-drilling technology with its many advantages is underused, and has not realized its full potential. Recent estimates(6) indicate that about 30% of all wells drilled in the U.S. could use air drilling successfully.

空気による粒体プラグの輸送

This paper describes behaviour of solid plugs pneumatically conveyed in a horizontal and vertical pipe whose purpose is to establish a basis for design of shch a conveying system, in which it is required to estimate the minimum air velocity, the velocity of the solid plug and the pressure loss of air. On the assumption that ideal flow of alternate solid plugs and air takes place, the minimum air velocity is obtained from force balance on the solid plug, and the plug velocity is also obtained from comparison of energy of air with that of the solid plug. The Ergun equation is adopted to compute the pressure loss of air passing through the solid plug. Computed results are favourably compared with results obtained from plug phase conveying for some polyethylene pellets. The particle diameter and its density, the voidage of the solid plug, the angle of internal friction and the frictional angle between the particle and the pipe wall are important. In this conveying system, there is an optimum air velocity at which the maximum power coefficient is reached, and the horizontal conveying is superior in power consumption to the vertical one.

Air velocity requirement for winnowing operations

An optimum air velocity range of 800–1300 ft/min, based upon extensive experimental results, was obtained for the winnowing of paddy grains with a 1·3 ft dia fan. By feeding grains and chaff separately and comparing the combined results with those for mixtures treated similarly, it was observed that there could be no possibility of any reduction in the air velocity requirement by increasing the height of free fall of grains and chaff above the air-stream; whereas with inclined feed, depending upon the type of chaff, there was both decrease and increase in this requirement, though these results were greatly modified when the grains and chaff were present in a mixture.

Drying of Heavily Salted Fish

The experimental drying of cut samples and of whole salt fish under various air conditions shows that the optimum air velocity is 100 to 125 cm. per second, air temperature 26 °C, and relative humidity 45 to 55 per cent. High drying potentials inhibit drying owing to the formation of an impervious salt-protein crust on the surface of the fish.The skin surface of the fish dries about 50 to 75 per cent as fast as the split surface. Under the recommended air conditions medium size salt codfish are dried from 130 per cent to 75 per cent, dry basis, moisture in about 40 hours.