Operating Air Flow Rate Research Articles

Prediction of pressure drop from multivariate polynomial regression for membrane-based air-to-air energy recovery ventilator cores

Ventilation is an active control method that can improve the indoor environment by removing indoor air pollution. The membrane-based air-to-air energy recovery ventilator is a ventilation device that utilizes the heat exchange between the discharged polluted air and fresh outdoor air during ventilation. This study analyzed the pressure drop characteristics of the ventilator core and aimed to develop an equation to predict the pressure drop using polynomial regression based on the size of the core, the airflow rate, and the opening ratio of the core. Within elements having the same opening ratio, the channel velocity (uc ) and equivalent pressure drop (Pe ) values showed a linear relationship, regardless of the element size. The opening ratio of the elements varied depending on the cell height. To analyze the correlation between the opening ratio of the element, substantial flow rate inside the element, and equivalent pressure drop, a multivariate polynomial regression analysis was conducted for the three variables. The difference between the values of the derived prediction formula and the experimental value was found to be within 5% across the entire range in which the experiment was conducted. Using the interaction formula of equivalent pressure drop, channel velocity, and opening ratio derived in this study, the pressure drop across the entire driving area could be predicted for an arbitrary cell height and width of the ventilator core, as well as the operating airflow rate.

Fine particle entrainment in fountain confined conical spouted beds

Many applications of the conical spouted beds involve operations using coarse and fine particle mixtures, which require high gas velocities due to the coarse particles, thereby leading to fine particle entrainment. In order to avoid entrainment, a new device has been proposed to confine the fountain. Thus, a study has been conducted on the influence the geometry and configuration of both confiner and draft tube have on particle entrainment, operating pressure drop, operating air flow rate and maximum cycle time. The results show that the fountain confiner greatly stabilises the operation and significantly reduces (above 50%) particle entrainment, but its influence on the other parameters is of rather low significance. Furthermore, the distance between the lower end of the device and the bed surface has a great impact on the performance of the spouted bed regime. Entrainment monitoring throughout time showed that its rate depends on the configuration, but remains constant with time.

Feasibility and economic evaluation of low-cost evaporative cooling system in fruit and vegetables storage

The climate of most zones of Ethiopia is characterized as high ambient temperature combined with low relative humidity, which has a negative effect on fruit and vegetables quality during harvesting, transportation, storage and marketing. Low-cost natural and forced ventilation evaporative coolers have been developed for fresh fruit and vegetables storage under arid and semi-arid conditions. The coolers were found to be effective in maintaining micro-environmental conditions for fresh fruit and vegetables storage. This research was aimed at investigating the feasibility and economics of using forced ventilation low-cost evaporative cooling to improve the indoor air conditions such as temperature and relative humidity. To reduce the indoor temperature and raise relative humidity, low-cost forced air ventilation evaporative cooler of 2.6 m2 floor area was fabricated and tested at Haramaya University, Fruit and Vegetables Research Station, on the storability of banana, papaya, orange, mandarin, lemon, mango, tomato and carrot. A fixed operating air flow rate of 4.3 kg- 1 was used to evaluate cooling performance and energy efficiency ratio of the cooler. The results showed that the indoor dry bulb temperature significantly (P < 0.001) drops parallel with a significant (P < 0.001) rise in relative humidity during storage. The energy efficiency ratio (varying from 55 to 84%) was found to be high as the evaporative cooling system requires small electric power only for operating fan and water pump. The economic analysis indicates that the payback period of the evaporative cooling system is less than 1.2 years. The results clearly demonstrate thatthe forced ventilation evaporative cooling system should be recommended for use in developing countries in order to maintain better quality of produce. These results demonstrated the relevance of the use of this low-cost adiabatic cooling technology for shelflife extension of fruits and vegetables and thereby encourage organized women groups to involve in this perishable commodity handling and processing as a source of income.Key words: Cooling, Fruits, Vegetables, Feasibility, Storage

A model for fluidized motion conveyor transporting fly ash

The performance characteristics of a 5.55 m length fluidized motion conveyor, transporting fly ash have been investigated in relation to the conveyor inclination. It is found that the haulage capacity of the conveyor at a particular operating air flow rate reduces with the decreased downward slope, whereas, the effect of operating air flow rate remains the same as reported earlier for 3.7 m conveyor length. No theoretical or empirical relation was found to predict the performance of the fluidized motion conveyors. Therefore, empirical model applicable to the design of air gravity conveyors for optimum yield was employed to predict the material mass flux, but the attempt was not successful. A novel model by incorporating additional parameters to the empirical relation pertinent to air gravity conveyor has been proposed to predict the performance of the fluidized motion conveyor. The prediction due to the improved model has shown a good agreement with the observed material mass flux. The proposed model also facilitates to determine a critical upward angle beyond which conveyor stops delivering material.

Liquid droplet behavior and instability in a polymer electrolyte fuel cell flow channel

A combined theoretical and experimental study of the influence of controllable engineering parameters, including surface PTFE (Teflon™) coverage (ranging from 5 to 20 wt.%), channel geometry, droplet chord length and height, and operational air flow rate, on liquid droplet deformation at the interface of the diffusion media (DM) and the gas flow channel was performed. The theoretical model reasonably predicts the measured contact angle hysteresis and identifies conditions under which the droplet tends toward an unstable state. The results presented in this study indicate that operational conditions, droplet height, chord length, channel size and level of surface hydrophobicity of the DM directly affect the droplet instability. Based on the analytical force balance model, the critical Reynolds number at which a droplet of given dimensions tends towards instability (i.e. may be removed from the channel) is predicted. Experimental data in both the stable and unstable regions as defined by the critical Reynolds number curve generally corresponds to the stability predictions. Empirical correlations relating surface tension and DM PTFE content were developed. At high flow rates, the surface hydrophobicity of the DM surface enhances efficacy of droplet removal, and may help to prevent local channel flooding. However, at low flow rates, hydrophobicity of the DM surface has only a minimal impact on efficacy of droplet removal and therefore high PTFE content may not be necessary, or desirable, since it also increases the electrical resistance of the system. It is also suggested that for constant air velocity and droplet size and shape, reduced channel height is preferred for effective water droplet removal where practical.