Double tube

Oxygen is suppHed quite routinely to patients suffering impaired respiratory function as weU as in other situations where oxygen is deemed to be useflil. The pure oxygen, with humidification, is deHvered via a simple double tube (cannula) to a point just inside the nostrils where the 99.5% gas blends with the room air (21% O2), and is inhaled. The concentration of oxygen that reaches the lungs thus depends on the rate and volume of air inhaled and on the exit flow of oxygen from the cannula, usually one to six L/min. 

Common practice is to specify exchanger surface in terms of total external square feet of tubing. The effective outside heat-transfer surface is based on the length of tubes measured between the inner faces of tube sheets. In most heat exchangers there is little difference between the total and the effective surface. Significant differences are usually found in high-pressure and double-tube-sheet designs. 

With double tube gas to water beat exchanger. Cooling water within manulacturer s standard conditions of temperature and pressure. 

The price of a shell and tube exchanger depends on the type of exchanger, i.e., fixed tube, U-tube, double tube sheets, and removable bundles. The tube side pressure, shell side pressure, and materials of construction also affect the price. If prices cannot be obtained from endors, correlating in-house data by plotting /fr vs. number of ft with correction factors for the variables that affect price will allow estimating with fair accuracy. If not enough in-house data is available to establish good correlations. it will be necessary to use the literature, such as References 16. 17. and 18. 

Nozu, S., Honda, H. and Nishida, S., Condensation ofZeotropic CFC114-CFC113 Refrigerant Mixture in the Annulus of a Double-Tube Coil with an Enhanced Inner Tube, Experimental Thermal and Fluid Science, Vol. 11, pp364-371, 1995. 

A thermohydraulic FW regulator has a double-tube control element located at the steam-water interface NOWL. The outer tube contains condensate and connects to a bellows. When the water level drops, the... 

The tube sheet forms the barrier between the shell and tube fluids, and where it is essential for safety or process reasons to prevent any possibility of intermixing due to leakage at the tube sheet joint, double tube-sheets can be used, with the space between the sheets vented Figure 12.16c. 

The above test provides a basis for evaluating a seal material s capability at the desired operating temperature. However, in realistic stack conditions, a seal material is under a shear stress. A double tube arrangement can be used to study the seal behavior. A disc can be sealed on both sides, and both tube enclosures can be pressurized to the same level. Such condition will eliminate the flexing of the membrane causing the seal to delaminate at a fairly low pressure when tested above Tg. In fact, a repeat test of the above seal with a double-tube arrangement showed that the seal could withstand 20 psi pressure before a small leak developed. 

Instructions can be found in the AOAC Official Methods of Analysis (Padmore, 1990, p. 69). A pointed corer consisting of a single or double tube, or slotted tube and rod, is used to remove a diagonal core from end to end of the horizontal bag. Bulk feeds should have ten or more cores from different regions. The sample should be stored in such a way that deterioration and change in composition are prevented (BS 5766, 1979). 

Welded double concentric tube or double tube sheet with tri-clamp sanitary fittings (tube side)... 

Component (auxiliary equipment) selection should be made with the assurance that it does not create a source for contamination intmsion. Heat exchangers should be double tube sheet or concentric tube design. 

Heat exchangers, other than the welded double-concentric-tube type or double-tube sheet type, must employ a pressure differential and a means for monitoring the differential. The pressure differential shall be such that the fluid requiring a higher microbial quality shall be that with the greater pressure. Written records of the pressure differential monitoring shall be maintained as required in 212.183... 

Figure 5.1 shows, conceptually, four commonly used types of heat transfer equipment, although many more refined designs of such equipment exist. On a smaller scale, a double-tube type is used, whereas on an industrial scale a shell-and-tube type heat exchanger is frequently used. 

Figure 5.1 Few common types of heat exchangers, (a) Double-tube type (b) shell-and-tube type (c) coil-type and (d) plate-type.

Thus, d for a narrow space between two parallel plates, of which b is sufficiently large compared withz, is almost equal to 2z. Values offluid flow through the annular space between the outer and inner tubes of the double tube-type heat exchanger or fluid flow outside and parallel to the tubes of multitubular heat exchanger can be calculated using Equation 5.11. 

Calculate the equivalent diameter of the annular space of a double tube-type heat exchanger. The outside diameter of the inner tube d is 4.0 cm and the inside diameter of the outer tube is 6.0 cm. 

MUk, flowing at 20001 h through the stainless steel inner tube (40 mm i.d., 2 mm thick) of a double tube-type heater, is to be heated from 10 to 85 °C by saturated steam condensing at 120 °C on the outer surface of the inner tube. Calculate the total length of the heating tube required. 

C. Double tube electrode. Double channel electrode. 

The double-tube still consists of an outer tube of air-supported transparent plastic... 

Inside the shell sits the tube bundle, in which the tubes are either brazed, welded, or rolled to a circular single or double tube sheet. Typical tube flow patterns are either one, two, four, or six passes. 

The chemical quality of the steam supplied to the still must be controlled to prevent recontamination of the distillate. Also, the condenser must be of a double-tube design to prevent condenser coolant from coming into direct contact with the distallate, thereby causing recontamination. 

T Tubular fluorescent lamp TC Tubular fluorescent compact lamp H High pressure HM High pressure mercury HI High pressure iodide HS High pressure sodium L Low pressure LS Low pressure sodium Q Quartz (halogen) lamp . T Tubular lamp . E Elliptical form (2) -D Double tube compact lamp -DE Double ended -L Long compact lamp -SE Self ballasted electronic -U U-shaped fluorescent lamp -Us U-shaped fluorescent lamp, short -EL Compact fluorescent lamp for external electronic ballast -with key letter T Tube diameter (in mm) (3) Lamp rated power (without ballast), in W. 

If mixing of the shell-side and tube-side fluids cannot be tolerated, then use the double tube-sheet design shown in Figure 4.4 for extra protection. Because... 

Figure 4.4 Double-tube sheet heat-exchanger design. From Ref. 18 with permission.

In the ICI gas-heated reformer (GHR) (Figure 49) the reformer tubes consist of an outer scabbard tube with an open ended bayonet tube inside, and the annular space between the tubes is filled with the reforming catalyst. The steam/natural gas mixture enters the tubes via a double tube sheet and flows downwards through the catalyst, and the reformed gas leaves through the bayonet tubes. To enhance the heat transfer from... 

Some simple heal transfer equipments consist of two concentric tubes, and are properly called double-tube heat exchangers (Fig. 8-27). In such devices, one fluid flows through the tube while the other flows through the aunular space. The governing differential equations for both flow.s are identical. I herefore, steady laminar flow through an annulus can he studied analytically by using suitable boundary conditions. 

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