Temperature dewpoint

Sf=Q at 233.15 K = —40 C. Converted and interpolated from Theimodynamic Vmpeities of KLea 60 (Britisli units, 20 pp.), copyright ICI Chemicals and Polymers Limited, 1993. Reproduced hy permission. Ty = huhhle point temperature Tg = dewpoint temperature. 

The total pressure thus has no importance. If this result is. sought from a Mollier diagram by finding the intersection of the humidity line (jr = humidity of air = constant) and the saturation curve, which gives the dewpoint temperature, a diagram constructed for a pressure of 9.S0 mbar should be used. A decent ap-proximation can be found from a diagram constructed for pressure p 1 bar. 

Saturated air is difficult to measure accurately a deviation of 3-5 K must be accepted. In some air conditioning systems, very humid air may condense on surfaces below the dewpoint temperature of the air. Poorly insulated ducts containing humid air can cause serious problems. See Fig. 9.57. 

The dewpoint hygrometer detects the dewpoint temperature of air by cooling a surface in contact with the air to the dewpoint temperature. There are several ways to achieve cooling and to observe the formation of condensate on the surface. The early dewpoint hygirometers were cooled simply by applying the vaporization of ether or some other suitable liquid. Condensate formation on the surface was determined visually. Other cooling methods are to use a refrigerant flow in direct or indirect contact with the back of the surface, or to use electricity with a (thermoelectric) Peltier element. 

The observation may be by a lamp illuminating the surface and a photocell to detect the scattered light due to the water droplets on the surface. The accurate measurement of the surface temperature, which is the dewpoint temperature, is critical. If a coolant is used, a close approximation for the surface temperature is the fluid temperature otherwise a small thermocouple or resistance sensor can be attached to or embedded into the surface. 

Even for this simplest CCGT plant, iterations on such a calculation are required, with various values of p, in order to meet the requirements set on T, the steam turbine entry temperature, and 7s (the calculated value of 7s has to be such that the dewpoint temperature of the gas (7jp) is below the economiser water entry temperature (7b) and that may not be achievable). But with the ratio /i satisfactorily determined, the work output from the lower cycle Wl can be estimated and the combined plant efficiency obtained from... 

The reason for using feed heating to set the entry feed water temperature at a level T, above the condenser temperature is that Tb must exceed the dewpoint temperature Tjp of the exhaust gases. If is below Tjp then condensation may occur on the outside of the economiser tubes (the temperature of the metal on the outside of the tubes is virtually the same as the internal water temperature because of the high heat transfer on the water side). With Tb > Tjp possible corrosion will be avoided. 

Hot water boilers are potentially more susceptible to gas-side corrosion than steam boilers due to the lower temperatures and pressures encountered on low- and medium-temperature hot water boilers. With low-temperature hot water especially, the water-return temperature may drop below the water dewpoint of 50°C, causing vapor in the products of combustion to condense. This, in turn, leads to corrosion if it persists for long periods. The remedy is to ensure that adequate mixing of the return water maintains the water in the shell above 65°C at all times. Also, if medium or heavy fuel oil is to be used for low- or medium-temperature applications it is desirable to keep the heat transfer surfaces above 130°C, this being the approximate acid dewpoint temperature of the combustion gases. It may be seen, therefore, how important it is to match the unit or range of unit sizes to the expected load. 

Several boilers discharging into a single-core chimney are to be avoided. At times of low load the efflux velocity will be very low, which, in turn, will allow the chimney to cool. This may then drop to dewpoint temperatures and, where sulfur is present in the fuel, acid will form. If the chimney is unprotected steel, it will suffer rapid corrosion. Even worse, as the boilers increase their load the efflux velocity will increase and start to discharge the acid droplets, which quickly fall out and cause damage to surrounding property. 

Dry bulb temperature Wet bulb temperature Dewpoint temperature Relative humidity... 

The temperature at which water vapor (steam) condenses. The dewpoint temperature is important in boiler fuel combustion processes, as whenever a metal surface is cooler than flue gas, condensation occurs. If sulfur gases are present and the acid dewpoint (the tem-... 

Polarization citrve for PEMFCs with two different cathode diffusion layers carbon fiber paper with one MPL and carbon fiber cloth with two MPLs. Operating conditions ceU temperature of 85°C, O2/H2 dewpoint temperatures of 90/100°C gas pressures of 2 atm. CFP DL was a TGP-H-090 with 20 wt% PTFE in the MPL. CCs were PWB-3 from Stackpole cathode CC had 15 wt% PTFE in the MPL near the CL and 30 wt% PTFE in the MPL near the flow field. The anode CC had 15 wt% PTFE in both MPLs carbon loading on the MPL was not specified. The catalyst Pt loading was 0.4 mg cm and the Nation loading was 1.1 mg cm for all catalyst layers the membrane was a Nation 115. (Modified from E. Antolini et al. Journal of Power Sources 163 (2006) 357-363. With permission from Elsevier.)... 

Gas specifications will be inqportant only if the gas is to be delivered to a gas pipeline system. If the gas is to be injected in the producing field the only usual critical requirement is to dehydrate the gas adequately to prevent hydrate formation anywhere in the system. The gas pipeline specification which most Influences the design of oil-gas separation systems is the hydrocarbon dewpoint limitation. This is usually expressed as a maximum dewpoint temperature at a specified pressure. For onshore gas pipelines in the USA end Europe this specification may be in the range of 32°F (0°C) at 1000 paia (68 atmospheres), which is adequate to prevent condensation of liquids in the pipelines in the normal range of onshore pipeline operating pressures from 900 to 1000 psl. In the USA this specification is seldom iiqposcd on producers and is controlled with pipeline facilities. 

The compressed refrigerant vapor is discharged from the compressor. This vapor is superheated, meaning that it is above its dewpoint temperature. 

DEW POINT. The temperature to which a given parcel of air must be cooled at constant pressure and constant watervapnr content in order for saturation to occur, ihc temperature at which the saturation vapor pressure of the parcel is equal tu the actual vapor pressure of ihc contained water vapor. Any further cooling usually results in the formation of dew or frost. Also called dewpoint temperature. When this temperature is below 0 C.. it is sometimes called the frost point. 

The response variables included virtually everything that one might observe in a real reactor — reactor maximum and outlet temperatures, reactor outlet concentrations of butyraldehyde, butanol, and byproducts, inlet and outlet dewpoint temperatures, catalyst productivity, reactor pressure drop, and so on. 

The same problem occurs on the hot side of the FEHE. As the hot reactor effluent is cooled, it starts to condense at some temperature. And this dewpoint temperature could occur in the heat exchanger and not in the flooded condenser if a large area is used. 

Calculate the temperature and composition of a liquid in equilibrium with a gas mixture containing lO.O mole% benzene, 10.0 mole% toluene, and the balance nitrogen (which may be considered noncondensable) at 1 atm. Is the calculated temperature a bubble-point or dewpoint temperature ... 

Toluene(l) and water(2) are essentially immiscible as liquids. Determine the dewpoint temperatures and the compositions of the first drops of liquid formed when vapor mixtures of these species with mole fractions Zi = 0.2 and Zi = 0.7 are cooled at the constant pressure of 101.33 kPa. What is the bubble-point temperature and the composition of the last drop of vapor in each case See Table 10.2, p. 346, for vapor-pressure equations. 

Single-Stage Flash Calculations 375 Bubblepoint Temperature and Pressure 376 Dewpoint Temperature and Pressure 377 Flash at Fixed Temperature and Pressure 377 Flash at Fixed Enthalpy and Pressure 377 Equilibria with Ks Dependent on Composition 377... 

Figure 4.24 General layout of the humidity chart showing die location of the wet-bulb and dry-bulb temperatures, the dew point and dewpoint temperature, and the adiabatic saturation line and wet-bulb line.

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