Unconditioned Air Research Articles

Longitudinal distribution of canine respiratory heat and water exchanges.

We assessed the longitudinal distribution of intra-airway heat and water exchanges and their effects on airway wall temperature by directly measuring respiratory fluctuations in airstream temperature and humidity, as well as airway wall temperature, at multiple sites along the airways of endotracheally intubated dogs. By comparing these axial thermal and water profiles, we have demonstrated that increasing minute ventilation of cold or warm dry air leads to 1) further penetration of unconditioned air into the lung, 2) a shift of the principal site of total respiratory heat loss from the trachea to the bronchi, and 3) alteration of the relative contributions of conductive and evaporative heat losses to local total (conductive plus evaporative) heat loss. These changes were not accurately reflected in global measurements of respiratory heat and water exchange made at the free end of the endotracheal tube. Raising the temperature of inspired dry air from frigid to near body temperature principally altered the mechanism of airway cooling but did not influence airway mucosal temperature substantially. When local heat loss was increased from both trachea and bronchi (by increasing minute ventilation), only the tracheal mucosal temperature fell appreciably (up to 4.0 degrees C), even though the rise in heat loss from the bronchi about doubled that in the trachea. Thus it appears that the bronchi are better able to resist changes in airway wall temperature than is the trachea. These data indicate that the sites, magnitudes, and mechanisms of respiratory heat loss vary appreciably with breathing pattern and inspired gas temperature and that these changes cannot be predicted from measurements made at the mouth. In addition, they demonstrate that local heat (and presumably, water) sources that replenish mucosal heat and water lost to the airstream are important in determining the degree of local airway cooling (and presumably, drying).

DEHUMIIDIPIER ASSISTED LARGE SCALE DEEP-BED DXYIAG OF GRAINS

ABSTRACT The performance of a compression refrigerating type dehumidifier /heat pump with controllable discharge air dry bulb temperature. was investigated. In one experiment, the dehumidifier was implemented into a large scale commercial soybean drying process. The experimental result was compared with the computer simulated result of unconditioned ambient air soybean drying (without the dehumidifier). The dehumidified and reheated air was found to be able to remove 743 kg of water from soybeans in a 24-hour period; while the ambient air could remove only 85 kg.