Câu 1: Tìm từ trong 2 câu thơ sau liên quan đến các từ: hình chiếu, tia chiếu, mặt phẳng chiếu.

The larger the Bi number, the more accurate the lumped system analysis. a)-True b)- False

mrs_skeptik [129]

Answer:

b). False

Explanation:

Lumped body analysis :

Lumped body analysis states that some bodies during heat transfer process remains uniform at all times. The temperature of these bodies is a function of temperature only. Therefor the heat transfer analysis based on such idea is called lumped body analysis.

Biot number is a dimensionless number which governs the heat transfer rate for a lumped body. Biot number is defined as the ratio of the convection transfer at the surface of the body to the conduction inside the body. the temperature difference will be uniform only when the Biot number is nearly equal to zero.

The lumped body analysis assumes that there exists a uniform temperature distribution within the body. This means that the conduction heat resistance should be zero. Thus the lumped body analysis is exact when biot number is zero.

In general it is assume that for a lumped body analysis, Biot number $\leq$ 0.1

Therefore, the smaller the Biot number, the more exact is the lumped system analysis.

7 0

3 years ago

Two steel plates of 15 mm thickness each are clamped together with an M14 x 2 hexagonal head bolt, a nut, and one 14R metric pla

Blababa [14]

Answer:

a) 50 mm

b) 808.24 MN/m

Explanation:

Given:

Thickness of each steel plate = 15mm

a) To find suitable length of bolt, we'll use:

Length of bolt = grip length + height of nut

To find the grip length since there is a washer, we'll use:

Grip length = plate thickness + washer thickness

Since we have 2 plates of 15mm thickness,

Plate thickness = 15 + 15 = 30mm

Using the table, a metric plain washer has a thickness of 3.5mm

Grip length = 30 + 3.5 =33.5 mm

Height of nut: Using table A-31, height of hexagonal nut is 12.8 mm

Therefore,

Length of bolt = 33.5 + 12.8 = 46.3

Rounde up to the nearest 5mm, we'll get 50mm

Length of bolt = 50mm

b) Bolt stiffness:

Threaded length for L ≤ 125mm

LT = 2*d + 6

Where d = 14mm, from table(8-7)

= 2*14 + 6

= 34 mm

Area of unthreaded portion:

Ad= $\frac{\pi}{4} d^2 = \frac{pi}{4} * 14^2 = 153.94 mm^2$

Length of unthreaded portion in grip:

Ld = 50 - 34 = 16mm

Length of threaded portion in grip:

Lt = 33.5 - 16 = 17.5mm

Bolt stiffness = $\frac{A_d A_t E}{A_d l_t + A_t l_d}$

$= \frac{153.94 * 115 * 207}{(153.94*17.5)+(115*16)} = 808.24$

Bolt stiffness = 808.24 MN/m

7 0

3 years ago

why is that most solidification does not begin until the temperature falls somewhat below the equilibrium melting temperature? p

Aleksandr [31]

Answer:

Otherwise dies may fail under high operating pressure and temperature. ... The better description and understanding of the phase change processes can be ... occurs only when the temperature is dropped well below the equilibrium temperatures. ... The solidification starts at the bottom and the solidified volume grows more

Explanation:

6 0

3 years ago

What is the importance of food handling machines in food industry (Explain in points).

klemol [59]

Answer:

Explanation:

Profile photo for Rosie Milojevic

Rosie Milojevic, Business Development at iComplied

Answered 3 years ago

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8 0

3 years ago

You have been assigned the task of reviewing the relief scenarios for a specific chemical reactor in your plant. You are current

postnew [5]

Answer:

$D=0.016m$