What is Wetted Perimeter? How is it calculated?

The wetting perimeter is the perimeter length of the fluid in contact with the pipe wall. For example, in the case of a round tube, the wetted perimeter is its circumference. The casing annulus is the sum of the circumference of the inner and outer tubes.

Suppose there is a set of tubes consisting of a large tube 57* with a small tube.

25* composition, with large pipe diameter d (outside) small pipe diameter d (inside).

The material liquid of a single pipe generally does not have the problem of material liquid residue, but the multi-pipe process is different, and the manufacture of the end cover of the body under the multi-pipe process is relatively complicated, because the partition divides the lower device cover into several areas.

Each small area is most susceptible to liquid residues or dead spots. In order to facilitate the discharge, the bottom of the discharge can be made into an inclined or grooved structure. In order to prevent the appearance of dead corners, there should be excessive rounded corners at the intervals. The ends of the partition must also be deburred and made to be excessively rounded.

Main technical parameters:

material medium, coconut aqueous solution; Water evaporation capacity: 3800kg h;

Feed mass fraction.

4%；Discharge mass fraction: 60%; Evaporation state parameter.

Structural features: the use of parallel flow feeding method, the final effect discharge, the end effect of the four pipe cycle feeding, the use of thermal compression technology, that is, the heat pump to suck the second effect of the second steam as part of the first effect of the heating heat source, the use of coil to preheat the material, the first stage of the use of the last effect of the secondary steam for preheating, the remaining secondary steam into the condenser.

is condensed. The above content reference: Encyclopedia - Wetting the periphery.

In the principle of chemical engineering, take casing as an example:

The casing has the concept of wetting periphery and annular flow cross-section.

If there is a set of pipes consisting of a large pipe 57* and a small pipe 25*, the diameter of the large pipe d (outer) and the small pipe diameter d (inner).

Annular flow cross-sectional area: the area contained in the inner diameter of the large tube and the outer diameter of the small tube.

Let the inner diameter of the large pipe be d2 and the outer diameter of the small tube be d1, and the title will obtain d2=, d1=25mm annular flow cross-sectional area s=the area of the inner diameter of the large pipe - the area of the outer diameter of the small pipe = (4)d2 2-(4)d1 2=

Wetting periphery = * (large tube inner diameter d2 + small tube outer diameter d1) = (52 + 25) = 242mm

The calculation formula of equivalent diameter (round tube) = inner diameter of large tube d2 - outer diameter of small tube d1 = 52-25 = 27mm equivalent diameter (non-circular tube) is different from the above, please refer to the literature for details.

Did you study chemical engineering? Do you want to ask about the length of the wetting perimeter.

The wetting perimeter refers to the perimeter length of the rubber code contact between the fluid and the pipe wall. For example, in the case of a round pipe, the perimeter of the wet pipe is its simple perimeter. The casing annulus is the sum of the circumference of the inner and outer tubes.

Let : 1/3 of the longest diameter d of the long circle be b. 1/3 of the widest diameter d perpendicular to the longest diameter d is a.

Then: the area of the long circle s=7ab. The perimeter length of the oblong circle (a+b) (3+ 3).

In the case of solid particles, the characteristic length is the diameter of the particle.

In the case of a liquid flow, for a round pipe, the length d is the diameter of the round pipe; For non-circular pipes, the length d is generally removed from the hydraulic diameter, which is four times the hydraulic radius. The hydraulic radius is calculated as the ratio of the wetted perimeter to the wetted perimeter, if the side lengths of a square section are a and b, then the hydraulic radius is ab 2(a+b). The irregular cross-section is the same.

If the fluid flows through a circular pipe, d is the equivalent diameter of the pipe. The Reynolds number can be used to distinguish whether the flow of a fluid is laminar or turbulent, and it can also be used to determine the resistance experienced by an object to flow in a fluid.

The feature length is generally the volume of the system divided by its surface.

In physics, feature length is the dimension that defines the scale of a physical system. The feature length is used as input to the formula, which can be used for certain characteristics of the system.

In the case of solid particles, the characteristic length is the diameter of the particle.

In the case of liquid flow, there are two cases, for a round pipe, the length d is the diameter of the round pipe;

For non-circular pipes, the length d is generally removed from the hydraulic diameter, which is four times the hydraulic radius.

The hydraulic radius is calculated as the ratio of the wetted perimeter to the wetted perimeter, and the answer is the Reynolds number, a dimensionless number that can be used to characterize the flow of a fluid. re= vd, where v, , and are the flow velocity, density, and viscosity coefficient of the fluid, respectively, and d is a characteristic length.

There are many kinds, which are simply sealed around the foundation pit with wooden boards and supported by supports. Prevent collapse on all sides;

There are also brick walls and concrete ones. There are also large excavation slopes.

The engineering quantity has its own algorithm, and it is calculated according to the actual situation.

Foundation pit enclosure refers to the enclosure frame with steel pipes on the four sides of the foundation, and the engineering quantity is calculated by the square.

Is it foundation pit enclosure or foundation pit support?

I haven't heard of the fence, which should literally be the guardrail.

If it's a support, there's a lot to count.

Foundation pit enclosure:

Foundation pit support is to ensure the safety of the underground structure construction and the surrounding environment of the foundation pit, the side wall of the foundation pit and the surrounding environment of the use of support, reinforcement and protection measures.

The People's Republic of China industry standard "Technical Regulations for Building Foundation Pit Support" JGJ120-2012 defines foundation pit support as follows:

In order to protect the safety of the construction of the underground main structure and the surrounding environment of the foundation pit, the temporary support, reinforcement, protection and groundwater control measures are adopted for the foundation pit.

The common foundation pit support types mainly include:

row pile support, pile support, pile anchor, row pile cantilever;

Underground diaphragm wall support, ground wall + support;

cement retaining walls;

4.Steel sheet pile: section steel pile cross baffle support, steel sheet pile support;

soil nailing wall (spray anchor support);

inverted arch wall; undisturbed soil grading;

foundation pit support;

piles, walls and support systems;

10.Simple horizontal support;

11.reinforced concrete row piles;

1. Proportion:

Refers to the proportion of each character, because the number of each character will be allocated according to the popularity of the character in a box.

2. Calculation of average price:

Divide the total price by the total number of boxes to get the average price.

Related introduction: Generally, when holding a box or holding a reward, the role of each box is fixed, such as 2 A, 2 B, 1 C, 1 D, so the proportion and number of characters in how many boxes are fixed, also called fixed ratio.