AN OPEN SYSTEM FOR PLANT GAS-EXCHANGE ANALYSIS

1974 ◽  
Vol 54 (1) ◽  
pp. 161-165
Author(s):  
C. L. BEADLE ◽  
K. R. STEVENSON ◽  
G. W. THURTELL ◽  
P. A. DUBÉ
Keyword(s):  
Water Vapor ◽  
Gas Exchange ◽  
Open System ◽  
Sampling Period ◽  
Lag Time ◽  
Dew Point ◽  
Gaseous Exchange ◽  
Sample Analysis ◽  
Valve System ◽  
Short Period

An open system was designed for studies of photosynthesis and transpiration on single leaves of crop plants. The system contained several features that facilitated the measurement of gaseous exchange between leaves and their environment. An inexpensive unit, requiring little attention, was developed to control the humidity of the influx air. Also, a system of solenoid valves was arranged to control the sequence of sample analysis. This allowed several cuvettes to be monitored sequentially in a short period of time. The valve system was designed to minimize lag time to obtain stable readings following valve activation. A 2-min sampling period was used for each cuvette. A dew-point hygrometer was used to measure water vapor content of the air. The dew-point hygrometer, designed for unattended outdoor use, was modified for cuvetting studies. The performance of the system is described and evaluated.

Heat and Mass Transfer in Double-Filmwise Heat Exchanger for Industrial Food Processing Applications

2011 ◽  
Author(s):  
Helen Skop ◽  
James Pezzuto ◽  
Valeriy G. Oleynikov-White ◽  
John F. Cavallo ◽  
Robert Fesjian
Keyword(s):  
Water Vapor ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Waste Heat ◽  
Cost Effective ◽  
Dew Point ◽  
Point Temperature ◽  
Dew Point Temperature ◽  
Gas Cooling ◽  
Stack Gas

The baking industry is considered as one of the major energy consuming food industries in North America. More than 40% of bakery fuel consumption is used to evaporate water in the processes [1]. In addition to the baking process’ vapor the oven stack gas contains water vapor from combustion products. Overall the content of water vapor in the typical oven stack gas is about 20% by volume. Most bakeries waste this vapor and its latent heat. Bakeries’ ovens have wide diversity in power and design. Off-the-shelve heat exchangers are not considered as cost effective equipment for stack gas cooling below gas’ dew point temperature. At typical oven stack gas composition water vapor condensation begins to condense at about 72° C. Not using the latent heat of stack water vapor and the heat from gas cooling from dew point temperature to ambient temperature results in low effectiveness of waste heat recovery. Mainly the effect from the recovery of stack gas cooling prior to condensation is considered as non cost effective and waste heat recovery is neglected.

Canopy Gas Exchange Measurements of Cotton in an Open System

2009 ◽  
Vol 101 (1) ◽  
pp. 52-59 ◽  
Author(s):  
Jeffrey T. Baker ◽  
Scott Van Pelt ◽  
Dennis C. Gitz ◽  
Paxton Payton ◽  
Robert Joseph Lascano ◽  
...  
Keyword(s):  
Gas Exchange ◽  
Open System

scholarly journals A new approach for flow-through respirometry measurements in humans

2010 ◽  
Vol 298 (6) ◽  
pp. R1571-R1579 ◽  
Author(s):  
Edward L. Melanson ◽  
Jan P. Ingebrigtsen ◽  
Audrey Bergouignan ◽  
Kazunori Ohkawara ◽  
Wendy M. Kohrt ◽  
...  
Keyword(s):  
Water Vapor ◽  
Relative Humidity ◽  
Gas Exchange ◽  
Flow Rate ◽  
Water Vapor Pressure ◽  
Propane Combustion ◽  
Pull System ◽  
Novel Approach ◽  
Flow Through ◽  
Combustion Tests

Indirect whole room calorimetry is commonly used in studies of human metabolism. These calorimeters can be configured as either push or pull systems. A major obstacle to accurately calculating gas exchange rates in a pull system is that the excurrent flow rate is increased above the incurrent flow rate, because the organism produces water vapor, which also dilutes the concentrations of respiratory gasses in the excurrent sample. A common approach to this problem is to dry the excurrent gasses prior to measurement, but if drying is incomplete, large errors in the calculated oxygen consumption will result. The other major potential source of error is fluctuations in the concentration of O2 and CO2 in the incurrent airstream. We describe a novel approach to measuring gas exchange using a pull-type whole room indirect calorimeter. Relative humidity and temperature of the incurrent and excurrent airstreams are measured continuously using high-precision, relative humidity and temperature sensors, permitting accurate measurement of water vapor pressure. The excurrent flow rates are then adjusted to eliminate the flow contribution from water vapor, and respiratory gas concentrations are adjusted to eliminate the effect of water vapor dilution. In addition, a novel switching approach is used that permits constant, uninterrupted measurement of the excurrent airstream while allowing frequent measurements of the incurrent airstream. To demonstrate the accuracy of this approach, we present the results of validation trials compared with our existing system and metabolic carts, as well as the results of standard propane combustion tests.

Automatic dew-point temperature sensor

1982 ◽  
Vol 52 (6) ◽  
pp. 1658-1660 ◽  
Author(s):  
H. Graichen ◽  
R. Rascati ◽  
R. R. Gonzalez
Keyword(s):  
Water Vapor ◽  
Vapor Pressure ◽  
Water Vapor Pressure ◽  
Skin Surface ◽  
Dew Point ◽  
Pressure Gradients ◽  
Point Temperature ◽  
Dew Point Temperature ◽  
Peltier Module ◽  
Local Water

A device is described for measuring dew-point temperature and water vapor pressure in small confined areas. The method is based on the deposition of water on a cooled surface when at dew-point temperature. A small Peltier module lowers the temperature of two electrically conductive plates. At dew point the insulating gap separating the plates becomes conductive as water vapor condenses. Sensors based on this principle can be made small and rugged and can be used for measuring directly the local water vapor pressure. They may be installed within a conventional ventilated sweat capsule used for measuring water vapor loss from the skin surface. A novel application is the measurement of the water vapor pressure gradients across layers of clothing worn by an exercising subject.

Gas exchange of Agropyron desertorum: diurnal patterns and responses to water vapor gradient and temperature

Oecologia ◽  
1988 ◽  
Vol 77 (3) ◽  
pp. 289-295 ◽  
Author(s):  
Robert S. Nowak ◽  
Jay E. Anderson ◽  
Nancee L. Toft
Keyword(s):  
Water Vapor ◽  
Gas Exchange ◽  
Agropyron Desertorum ◽  
Diurnal Patterns

scholarly journals Sample drying to improve HCHO measurements by PTR-MS instruments: laboratory and field measurements

2009 ◽  
Vol 9 (5) ◽  
pp. 19845-19877 ◽  
Author(s):  
B. T. Jobson ◽  
J. K. McCoskey
Keyword(s):  
Water Vapor ◽  
Field Measurements ◽  
Field Testing ◽  
Water Soluble ◽  
Dew Point ◽  
Cold Trap ◽  
Ice Surface ◽  
Quasi Liquid Layer ◽  
Significant Uptake ◽  
Humidity Dependence

Abstract. A significant improvement in the PTR-MS instrument sensitivity to formaldehyde was obtained by drying the air sample to a dew point of −30°C using a cold trap to condense and freeze water vapor. At warmer trap temperatures there was significant uptake of formaldehyde and other water soluble organics, suggesting the presence of a quasi-liquid layer on the ice surface. By removing water vapor to a low constant dew point, the PTR-MS can be operated at low E/N ratios, significantly increasing normalized sensitivities for all organics and removing their humidity dependence due to reactions with H+(H2O)2. At an E/N ratio of 80 Td the formaldehyde normalized sensitivity was 25 Hz/ppbv per MHz H3O+ with an estimated detection limit of 78 pptv. Field testing demonstrated good agreement between HCHO measurements made at ambient humidity and corrected for water vapor effects compared to dehumidified sampling at −30°C. Field testing also revealed that at an E/N ratio of 100 Td or lower there was a significant ion signal at m/z=49, likely CH3OOH. Sampling drying and operation at low E/N ratios enables sensitive measurements of HCHO and potentially CH3OOH, both important tropospheric photoproducts.

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