Surface Dew Point and Water Vapor Aloft

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.

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Automatic dew-point temperature sensor

Journal of Applied Physiology ◽

10.1152/jappl.1982.52.6.1658 ◽

1982 ◽

Vol 52 (6) ◽

pp. 1658-1660 ◽

Cited By ~ 46

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.

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

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-9-19845-2009 ◽

2009 ◽

Vol 9 (5) ◽

pp. 19845-19877 ◽

Cited By ~ 3

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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Studi Penambahan Etilena Glikol dalam Menghambat Pembentukan Metana Hidrat pada Proses Pemurnian Gas Alam

Jurnal Rekayasa Proses ◽

10.22146/jrekpros.59871 ◽

2020 ◽

Vol 14 (2) ◽

pp. 198

Author(s):

Muslikhin Hidayat ◽

Danang Tri Hartanto ◽

Muhammad Mufti Azis ◽

Sutijan Sutijan

Keyword(s):

Water Vapor ◽

Low Temperature ◽

Natural Gas ◽

Operating Temperature ◽

Hydrate Formation ◽

Control Unit ◽

Dew Point ◽

Heavy Hydrocarbon ◽

Aspen Hysys ◽

Point Control

The gas processing facilities are designed to significantly reduce the impurities such as water vapor, heavy hydrocarbon, carbon dioxide, carbonyl sulfide (COS), benzene-toluene-xylene (BTX), mercaptane, and the sulfur compounds. A small amount of those compounds in natural gas is not preferable since they disturb the next processes. It was proposed to decrease natural gas's operating temperature to -20 ⁰F to remove the impurities from natural gas. The decrease of the natural gas's operating temperature has some consequences to the gas mixers such as hydrate formation at high pressure and low temperature, solidification of ethylene glycol (EG) solution, and the icing of the surface due to low temperature on the surface of chiller (three constraints). The Aspen Hysys 8.8 was used to obtain the suitable flowrate and concentration of the EG solution injected into the natural gas. Peng-Robinson's model was considered the most appropriate thermodynamic property model, and thus it has been applied for this research. The calculation results showed that the EG solution injection would reduce the hydrate formation due to water vapor absorption in the natural gas by EG. The EG solution's flowrate and concentration were varied from 20,000-2,000,000 lb/hr and 80-90 wt.%. When the separation was carried out at the operating temperature of -20 ⁰F, the EG solution's concentration fulfilling the requirement was of 80-84 wt.% with the flowrate of EG solution of 900,000 lb/hr and even more. This amount is not operable. More focused investigation was done for the variation of the operating temperature. Increasing operating temperature significantly reduced the flowrate of EG solution to about 200,000 lb/hr. An alternative process was proposed by focusing on two concentration cases of 80 and 85 % of weight at the low flow rate of EG solution, respectively. These simulations were intended to predict impurities' concentration in the effluent of Dew Point Control Unit (DPCU). The concentrations of BTX, heavy hydrocarbon, mercaptane, and COS flowing out of DPCU were 428.1 ppm, 378.4 ppm, 104 ppm, and 13.3 ppm, respectively. The concentrations of BTX and heavy hydrocarbon are greater than the minimum standard required. It is needed to install an absorber to absorb BTX and heavy hydrocarbon. However, the absorber capacity will be much smaller than if the temperature of natural gas is not decreased and not injected by the EG solution.Keywords: DPCU gas treatment; ethylene glycol solution; hydrate formation; simulationA B S T R A KUnit pengolahan gas dirancang untuk mengurangi sebagian besar senyawa pengotor seperti uap air, hidrokarbon berat, karbon dioksida, karbonil sulfida (COS), benzena-toluena-xilena (BTX), merkaptan, dan senyawa sulfur lainnya. Keberadaan senyawa tersebut dalam gas alam berbahaya karena mengganggu proses selanjutnya walaupun dalam jumlah sedikit. Untuk membersihkan gas alam dari senyawa pengotor, maka suhu operasi gas diturunkan menjadi -20 °F. Penurunan suhu operasi gas dapat menyebabkan pembentukan hidrat pada tekanan tinggi dan suhu rendah, pembekuan larutan etilena glikol (EG), dan pembentukan lapisan es pada permukaan chiller. Aspen Hysys 8.8 digunakan untuk memperkirakan berapa kecepatan alir dan konsentrasi larutan EG yang diinjeksikan ke gas alam. Model Peng-Robinson adalah model termodinamika yang diterapkan untuk penelitian ini. Hasil simulasi menunjukkan bahwa injeksi larutan EG dapat mengurangi pembentukan hidrat karena larutan EG menyerap uap air dalam gas alam. Kecepatan alir dan konsentrasi larutan EG divariasikan dari 20.000-2.000.000 lb/jam dan 80-90 % (%b/b). Saat pemisahan dilakukan pada suhu operasi -20 °F, konsentrasi larutan EG yang memenuhi syarat adalah 80-84 % (%b/b) dengan kecepatan alir larutan EG 900.000 lb/jam atau lebih. Jumlah ini sangat banyak dan kurang layak untuk dioperasikan. Penelitian difokuskan pada variasi suhu operasi. Peningkatan suhu operasi diikuti dengan pengurangan kecepatan aliran larutan EG secara signifikan yaitu menjadi sekitar 200.000 lb/jam. Alternatif proses diusulkan dengan berfokus pada penggunaan kecepatan alir larutan EG yang rendah dengan konsentrasi larutan EG sebesar 80 dan 85 % (%b/b). Simulasi dapat memprediksi konsentrasi pengotor yang keluar dari Dew Point Control Unit (DPCU). Konsentrasi BTX, hidrokarbon berat, merkaptan, dan COS yang mengalir keluar dari DPCU berturut-turut adalah 428,1 ppm, 378,4 ppm, 104 ppm, dan 13,3 ppm. Konsentrasi BTX dan hidrokarbon berat tersebut lebih besar dari standar minimum yang disyaratkan. Oleh karena itu, diperlukan pemasangan absorber untuk menyerap BTX dan hidrokarbon berat. Namun, kapasitas absorber akan jauh lebih kecil apabila dibandingkan dengan kondisi tanpa menurunkan suhu dan menginjeksikan oleh larutan EG.Kata kunci: DPCU; larutan etilena glikol; pembentukan hidrat; simulasi

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Chart of Air-Vapor Mixture Properties at Different Pressures

Journal of Applied Mechanics ◽

10.1115/1.4009083 ◽

1941 ◽

Vol 8 (1) ◽

pp. A14-A16

Author(s):

R. C. Binder

Keyword(s):

Water Vapor ◽

Relative Humidity ◽

Total Pressure ◽

Limited Range ◽

Dew Point ◽

Specific Humidity ◽

Vapor Mixture ◽

Close Approximation ◽

Point Temperature ◽

Dew Point Temperature

Abstract A discussion is given of the use of a total pressure-temperature diagram provided with reversible adiabatic and specific-humidity lines for mixtures of air and water vapor. The graphical relation between dew-point temperature, dry-bulb temperature, and specific humidity is given directly for any total pressure on this chart. From this relation the vapor pressure and relative humidity can be easily calculated. Certain chart lines give a close approximation to the wet-bulb temperature for a limited range. This pressure-temperature chart should be convenient and useful for a wide variety of problems which involve these fundamental thermodynamic properties.

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Water vapor isotopologues (H216O, H218O and HD16O) by ground-based FTIR spectroscopy in central Mexico

10.5194/egusphere-egu21-13433 ◽

2021 ◽

Author(s):

Alain Zuber ◽

Wolfgang Stremme ◽

Adolfo Magaldi ◽

Michel Grutter ◽

Caludia Rivera ◽

...

Keyword(s):

Water Vapor ◽

Ftir Spectroscopy ◽

Hydrological Cycle ◽

Isotopic Ratio ◽

Dew Point ◽

Central Mexico ◽

Isotopic Ratios ◽

Solar Absorption ◽

Rain Season ◽

The Relationship

Knowledge about water vapor isotopologues is a useful tool in the study of the hydrological cycle. Total columns of water vapor isotopologues (H216O, H218O and HD16O) are measured by ground-based solar absorption FTIR spectroscopy at Altzomoni (3985 m.a.s.l, 19.12&#186;N, 98.66&#186;W), a high altitude subtropical remote background site in central Mexico (Barthlott et al., 2017). In the contribution we present the time series of the isotopic composition of water vapor columns and profiles above central Mexico and analyze differences in the isotopic ratios of H216O, H218O and HD16O between the rain and dry seasons of the year: in the rain season, changes in the isotopic ratios might be dominated by the diurnal cycle, which correlates with the relative humidity, temperature and dew point, while isotopic ratio in the dry season might depend more on the origin of the air parcels and transportation. We discuss the hydrological cycle in central Mexico using the relationship between light and heavy isotopes, and how this relationship gives valuable information about the pathways, sources and transport.

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