# 2.) A plane wall is made of brick with a thermal conductivity of 1.5 W/(m⸳K). The wall is 20 cm thick and has a surface area of 10 m2 . One side of the wall is exposed to outside air blowing against the wall resulting in a heat transfer coefficient of 20 W/(m2 ⸳K). The other side is exposed to an air-conditioned room with a convective heat transfer coefficient of 5 W/(m2 ⸳K). a. What are the thermal resistances corresponding to conduction through the wall and convection at each wall surface? b. For every 1 o C of temperature difference between the outside and inside air, how much additional cooling power is required from the air conditioner?

The answers to the question are

a. The thermal resistances corresponding to conduction through the wall and convection at each wall surface is 2.167×10^(-2)

b. 46.15 W. That is for every 1 °C of temperature difference between the outside and inside air, 46.15 W additional cooling power is required from the air conditioner.

Explanation:

For a wall with convective heat transfer on either side, the total thermal resistance is given by

R = (1/(h1×A) + L/(A×k) + 1/(h2×A))

Where R = Total thermal resistance

h1 = 20 W/(m2×K)

h2 = 5 W/(m2×K)

A = Wall surface area = 10 m^2

L = Wall thickness = 20 cm = 0.2 m

Therefore, R = 2.167×10^(-2)

(b) The heat transferred for every 1 °C difference between the inside and outside temperatures is given by

Q = (T2 - T1)/R where T2 and T1 are the inside and outside temperatures respectively. Hence for (T2 - T1) = 1 °C we have

Q = (1 °C/2.167×10^(-2)) = 46.15 W

## Related Questions

A flow of 100 mgd is to be developed from a 190-mi^2 watershed. At the flow line the area's reservoir is estimated to cover 3900 acres. The annual rainfall is 40 in. the annual runoff is 14 in. and the annual evaporation is 49 in. 1. Find the net gain or loss in storage this represents.
2. Calculate the volume of water evaporated in acre* ft and cubic meters.

13-mi 27 acres

Explanation:

Suppose you are designing a sliding window protocol for a 1 Mbps point-to-point link to the moon, which has a one-way latency of 1.25 seconds. Assume that each frame carries 1 KB of data. (a) How many frames need to be in transit to keep this pipe full? (b) What is the maximum reasonable size for SWS and RWS needed for such a system? (c) For the SWS and RWS sizes found in part b, what is the number of bits needed for the sequence number?

approx 306 frames need to be in transit to keep this pipe full

maximum reasonable size is 306 frames

sequence number = 10 bit

Explanation:

given data

transmission rate = 1 Mbps

size of frame Tt = 1 KB

one way latency Tp = 1.25 s

to find out

How many frames need and What is the maximum reasonable size for SWS and RWS and what is the number of bits needed for the sequence number

solution

we know useful time is =

so total time is

total time = Tt + 2Tp

total time = + 2 × 1.25

so

possible frames are

≤ 1

n ≤ 1 +

n ≤ 306.17

so approx 306 frames need to be in transit to keep this pipe full

and

we know here

size of sending window is equal to size of receiving window

so maximum reasonable size is 306 frames

and

bit need for sequence number is

sequence number =

sequence number = 10 bit

A water pipe with a 5 cm inner diameter is designed for to have a flow rate of 75 Umin. What is the entrance length for this pipe (in cm)?

121.20 cm

Explanation:

Given data in question

inner dia = 5 cm

flow rate = 75  umin = 1.25 ×10³ cm³/sec

Solution

First we calculate Re by this formula

Re=  =

Re=

here we know Q is flow rate and D is dia of pipe and v is kinematic viscosity that is 1.14 × cm ² / sec

so Re=

Re =

So Re will be 27936 that is greater than 4000 thats why it is turbulent flow

and we know ≡ 4.4

so ≡ 24.24

length will be 121.20 cm

In the fluid-flow analogy for electrical circuits, what is analogous to a conductor? In the fluid-flow analogy for electrical circuits, what is analogous to a conductor?
An opened valve
A pump
A fluid
A closed valve
A frictionless pipe
A constriction in a pipe

I am going to say a pump

The principal application of high-speed steel is (a)- cutting tools (b)- internal combustion engine block (c) rails for high-speed trains (d) turbine blades

(a)- cutting tools

Explanation:

High speed steel is the cutting tool material .It is widely used in the production process.it also represent as HSS.High speed steel is made from heat treatment process of steel .

The high speed steel have following compositions

1.Tungsten - 18 %

2.Chromium - 4%

4.Carbon - 0.7 %

5.Iron - 76.3 %

So the option a is correct.

(a)- cutting tools

Why is it important (in the context of systems engineering management) to become familiar with analytical methods? Provides some specific examples.

Explained

Explanation:

Analytical methods are used for Risk management in the system's engineering department and it is therefore, important to be familiar with it. Many processes and practices such as identifying, measuring, managing risks in engineering systems are done using these analytical methods. In all types of systems analytical methods such as analyzing and measuring are needed. It also helps in risk aversion and risk reduction by balancing risk. Also the decision making is becomes better when these methods are employed. In advanced as well as  traditional systems there is a need to manage risk and these methods are always beneficial in doing that.

A coil of wire 8.6 cm in diameter has 15 turns and carries a current of 2.7 A. The coil is placed in a magnetic field of 0.56 T. What is the magnitude of the maximum torque that can be applied to the coil by the magnetic field?

Explanation:

it is given that diameter = 8.6 cm

current =2.7 ampere

number of turns = 15

magnetic field =0.56 T

maximum torque= BINASINΘ  for maximum torque sinΘ=1

so maximum torque==0.56×2.7×0.005806×15=0.13174 Nm

A sand has a natural water content of 5% and bulk unit weight of 18.0 kN/m3. The void ratios corresponding to the densest and loosest state of this soil are 0.51 and 0.87. Find the relative density and degree of saturation.

Relative density = 0.545

Degree of saturation = 24.77%

Explanation:

Data provided in the question:

Water content, w = 5%

Bulk unit weight = 18.0 kN/m³

Void ratio in the densest state, = 0.51

Void ratio in the loosest state, = 0.87

Now,

Dry density,

= 17.14 kN/m³

Also,

here, G = Specific gravity = 2.7 for sand

or

e = 0.545

Relative density =

=

= 0.902

Also,

Se = wG

here,

S is the degree of saturation

therefore,

S(0.545) = (0.05)()2.7

or

S = 0.2477

or

S = 0.2477 × 100% = 24.77%

A material point in equilibrium has 1 independent component of shear stress in the xz plane. a)True b)- False