1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
kotegsom [21]
3 years ago
7

A double-pane insulated window consists of two 1 cm thick pieces of glass separated by a 1.8 cm layer of air. The window measure

s 4 m in width and 3 m in height. The inside air is at 27ºC with a convection coefficient of 12 W/m2K, and the outer surface of the glass is at -10ºC. (a) Sketch the thermal circuit. (b) Find the temperature of the glass surface inside the room. (c) Calculate the heat loss through the window. (d) Which, if any, thermal resistances are negligible (less than 1% of the total)?

Engineering
1 answer:
Elanso [62]3 years ago
8 0

Answer:

(b). T = 22.55 ⁰C

(c). q = 557.8 W

Explanation:

we take follow a step by step process to solving this problem.

from the question, we have that

The two glass pieces is separated by a 1.8 cm distance layer of air.

the thickness of glass piece is 1 cm

width = 4 m

the height = 3 m

(a). the sketch of the thermal circuit is uploaded in the picture below.

(b).  the thermal resistance due to the conduction in the first glass plane is given thus;

R₁ = Lg / Kg A ................(1)

given that Kg rep. the thermal conductivity of the glass plane

A = conduction surface area

Lg = Thickness of glass plane4

taking the thermal conductivity of glass plane as Kg = 0.78 w/mk

inputting values into equation (1) we have,

R₁ = [1 (cm) ˣ 1 (m)/100 (cm)] / [(0.78 w/mk)(4m ˣ 3m)]

R₁ = 1.068 ˣ 10 ⁻³ k/w

Being that we have same thermal resistance in the first and second plane,

therefore R₁ = R₃ = 1.068 ˣ 10 ⁻³ k/w

⇒ Also the thermal resistance between air and glass as a result of the conduction by the layer is given thus

R₂ = La/KaA .....................(2)

given Ka = thermal conductivity of air

A = surface area

La = thickness of air

substituting values into the equation we have

R₂ = [1.8 (cm) ˣ 1 (m)/100 (cm)] / [(0.0262 w/mk)(4m ˣ 3m)]

R₂ = 5.73 ˣ 10⁻² k/w

Given the thermal resistance on the outer surface due to convection, we have

R₄ = 1/hA

inputting value gives R₄ = 1 / (12 w/m² ˣ 12m) = 6.94 ˣ 10⁻³k/w

R₄ = 6.94 ˣ 10⁻³k/w

Finally the sum total of thermal resistance = R₁ + R₂ + R₃ + R₄

R-total = 0.0663 kw

From this we can calculate the rate of heat loss

using  q = Ti - To / R-total ..............(3)

given Ti and To is the inside and outside temperature i.e. 27⁰C and -10⁰C

from equation (3),

q = 27- (-10) / 0.0063 = 557.8 W

q = 557.8 W  

⇒ Applying the heat transfer formula for inside surface glass temperature gives;

q = Ti - T₂ / R₃ + R₄

T₂ = Ti - q (R₃ + R₄)

T₂ = 27 - 557.8 (1.068ˣ10⁻³ + 6.94ˣ10⁻³ ) = 22.55°C

T₂ = 22.55°C

cheers i hope this helps

You might be interested in
A steady stream (1000 kg/hr) of air flows through a compressor, entering at (300 K, 0.1 MPa) and leaving at (425 K, 1 MPa). The
AleksandrR [38]

Answer:

The work furnished by the compressor is 69.77kJ/s

The minimum work required for the state to change is 55.26kW

Explanation:

The explanation to these solution is on the first, second , third and fourth uploaded image respectively

8 0
2 years ago
A manometer containing a fluid with a density of 60 lbm/ft3 is attached to a tank filled with air. If the gage pressure of the a
8090 [49]

Answer:

The fluid level difference in the manometer arm = 22.56 ft.

Explanation:

Assumption: The fluid in the manometer is incompressible, that is, its density is constant.

The fluid level difference between the two arms of the manometer gives the gage pressure of the air in the tank.

And P(gage) = ρgh

ρ = density of the manometer fluid = 60 lbm/ft³

g = acceleration due to gravity = 32.2 ft/s²

ρg = 60 × 32.2 = 1932 lbm/ft²s²

ρg = 1932 lbm/ft²s² × 1lbf.s²/32.2lbm.ft = 60 lbf/ft³

h = fluid level difference between the two arms of the manometer = ?

P(gage) = 9.4 psig = 9.4 × 144 = 1353.6 lbf/ft²

1353.6 = ρg × h = 60 lbf/ft³ × h

h = 1353.6/60 = 22.56 ft

A diagrammatic representation of this setup is presented in the attached image.

Hope this helps!

5 0
3 years ago
Match the word with the definition:
aksik [14]

1. Renewable Resources  = (Renewable means you can keep making it) =  resources that can be replenished (such as trees)

2. Nonrenewable Resources  =  ( Nonrenewable means it can't be made once it is used up) = resources that are gone once they are used (such as fossil fuels)

3. Producer  =  ( produces something) = person who makes goods or provides services

4. Consumer  = ( uses something) =   person whose wants are satisfied by using goods and services

5. Allocate  = ( put someplace) =   distribute

6. Choice =  option

7 0
3 years ago
Read 2 more answers
Two vertical, parallel clean glass plates are spaced a distance of 2mm apart. if the plates are placed in water, how high will t
Ulleksa [173]

Answer with Explanation:

The capillary rise in 2 parallel plates immersed in a liquid is given by the formula

h=\frac{2\sigma cos(\alpha )}{\rho gd}

where

\sigma is the surface tension of the liquid

\alpha is the contact angle of the liquid

\rho is density of liquid

'g' is acceleratioj due to gravity

'd' is seperation between thje plates

Part a) When the liquid is water:

For water and glass we have

\sigma =7.28\times 10^{-2}N/m

\alpha =0

\rho _{w}=1000kg/m^3

Applying the values we get

h=\frac{2\times 7.28\times 10^{-2}cos(0)}{1000\times 9.81\times 2\times 10^{-3}}=7.39mm

Part b) When the liquid is mercury:

For mercury and glass we have

\sigma =485.5\times 10^{-3}N/m

\alpha =138^o

\rho _{w}=13.6\times 10^{3}kg/m^3

Applying the values we get

h=\frac{2\times 485.5\times 10^{-3}cos(138)}{13.6\times 1000\times 9.81\times 2\times 10^{-3}}=-2.704mm

The negative sign indicates that there is depression in mercury in the tube.

4 0
3 years ago
Does anybody want 20 points? They're free get 'em while ya can...
DedPeter [7]

Answer:

hi

Explanation:

4 0
2 years ago
Read 2 more answers
Other questions:
  • A computer has a two-level cache. Suppose that 60% of the memory references hit on the first level cache, 35% hit on the second
    12·1 answer
  • What are the two most important things to remember when at the end of your interview?
    6·1 answer
  • A wall in a house contains a single window. The window consists of a single pane of glass whose area is 0.15 m2 and whose thickn
    10·1 answer
  • Which of the following refers to a full-scale version of a product used to validate performance?
    10·2 answers
  • From the information generated in Prob. 6.4 (from your previous Aero HW#1), calculate the maximum rate of climb for the single-e
    13·1 answer
  • Consider the experiment of Problem 1.27, in which a frictionless puck is sliding straight across a rotating turntable through th
    10·1 answer
  • A well-established way of power generation involves the utilization of geothermal energy-the energy of hot water that exists nat
    9·1 answer
  • What are practical considerations you might encounter when you increase the moment of inertia (I) while keeping the cross-sectio
    13·1 answer
  • Why is data driven analytics of interest to companies?
    9·1 answer
  • 1) Plastics that soften when heated,harden when cooled, and then can be heated and softened many times
    6·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!