Experimental and Numerical Study on Effects of Airflow and Aqueous Ammonium Solution Temperature on Ammonia Mass Transfer Coefficient

Abstract

This paper reports the results of an investigation, based on fundamental fluid dynamics and mass transfer theory, carried out to obtain a general understanding of ammonia mass transfer from an emission surface. The effects of airflow and aqueous ammonium solution temperature on ammonia mass transfer are investigated by using computational fluid dynamics (CFD) modeling and by a mechanism modeling using dissociation constant and Henry's constant models based on the parameters measured in the experiments performed in a wind tunnel. The validated CFD model by experimental data is used to investigate the surface concentration distribution and mass transfer coefficient at different temperatures and velocities for which the Reynolds number is from 1.36 ϫ 10 4 to 5.43 ϫ 10 4 (based on wind tunnel length). The surface concentration increases as velocity decreases and varies greatly along the airflow direction on the emission surface. The average mass transfer coefficient increases with higher velocity and turbulence intensity. However, the mass transfer coefficient estimated by CFD simulation is consistently larger than the calculated one by the method using dissociation constant and Henry's constant models. In addition, the results show that the liquid-air temperature difference has little impact on the simulated mass transfer coefficient by CFD modeling, whereas the mass transfer coefficient increases with higher liquid temperature using the other method under the conditions that the liquid temperature is lower than the air temperature. Although there are differences of mass transfer coefficients between these two methods, the mass transfer coefficients determined by these two methods are significantly related. INTRODUCTIONAmmonia (NH 3 ) emission not only leads to poor air quality in livestock buildings but also causes environmental acidification, 1 which will seriously impact the environment and natural sensitive ecosystem. NH 3 emissions and deposition to terrestrial and aquatic ecosystems have increased nearly 4-fold in the past 135 yr. 2 This research indicated that much of the increase has been associated with an increase in agriculture activities, especially with respect to the animal productions. Around 75% of European NH 3 emission comes from livestock productions, 3 and 80% of NH 3 emission in the United States is from domestic animal waste. 4 Therefore, NH 3 emission should be well controlled and a better understanding of the processes underlying NH 3 emission remains an important research topic.Evidence from various investigations and systematic studies suggests that environmental and manure properties have important impacts on NH 3 emission and the mass transfer coefficient. 5-7 These studies were mainly conducted by experiments using small-scale environmental chambers or wind tunnel devices. Mechanistic models of NH 3 release were reviewed according to 30 available research reports. 5 A laboratory investigation was reported concerning the impact of NH 3 emission due to the liquid-air temperature d...

New Insights into the Hourly Manure Coverage Proportion on the Manure Belt in a Typical Layer House for Accurate Ammonia Emission Modeling

“…It is extremely difficult to exactly measure the surface area of the manure due to its irregular shape, but the projected manure area still represents a suitable method to approximate the surface area since the release of ammonia from manure is significantly affected by the airflow characteristics (including temperature, velocity, turbulence, etc.) above the release surface according to previous studies [ 14 ]. Therefore, manure covered underneath has a limited contribution to the total emissions and the projected area would not be considerably different from the true surface area since the height of the overlap is not large according to the field observation.…”

“…Therefore, it is crucial to understand and model the ammonia emissions in poultry houses so as to provide information to develop appropriate mitigation and management strategies. Much work had been done to predict ammonia release from manure [ 13 , 14 , 15 , 16 , 17 ], and several types of models were developed in the literature, including statistical models [ 18 , 19 ], balance models [ 20 , 21 ], and process-based models [ 22 , 23 ]. More recently, Tong et al [ 24 ] developed a mechanistic model, which was based on the fundamental understanding of physical and biochemical processes of ammonia emissions from manure, to estimate the emissions rate ( , mg ) from laying hen manure.…”

Research progress on animal environment and welfare

“…The main purpose of a livestock building is to establish and sustain an appropriate microclimatic environment for the animals. Among the numerous environmental factors that require regulation in livestock buildings, air quality and its associated parameters are commonly regarded as crucial [17,18]. To determine the comfort thresholds of temperature, relative humidity, wind speed, and concentrations of CO 2 and NH 3 for laying hens, relevant references were examined and the findings are summarized in Table 1 [19].…”

An integrated device for rapid analysis of indoor air quality in farms: The cases of milking parlors and greenhouses for baby leaf cultivation

“…As widely known, NH3 emission is influenced by temperature and humidity. Moreover, the effect of ventilation must also be considered since it influences the emission rate (Rong et al, 2010), although this does not necessarily lead to an increase in air concentrations because the natural or forced ventilation favors its removal from the building (Bleizgys and Bagdoniene, 2016;Herbut and Angrecka, 2014).…”