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3 years ago

A pan of ice is placed over a flame.

1 answer:

8 0

A. The molecules start packed together very tightly in a solid. Then when it turns to water, the molecules can move around each other freely, but still contained. When water turns to vapor, the molecules are going crazy moving around. They are not contained at all and bounce of of each other freely.

b. The temperature rises. (ice turns to water at 33 degrees and water turns to vapor at 212 degrees)

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Steam is to be condensed on the shell side of a heat exchanger at 150 oF. Cooling water enters the tubes at 60 oF at a rate of 4

zalisa [80]

Answer:

a. 572Btu/s

b.0.1483Btu/s.R

Explanation:

a.Assume a steady state operation, KE and PE are both neglected and fluids properties are constant.

From table A-3E, the specific heat of water is $c_p=1.0\ Btu/lbm.F$ , and the steam properties as, A-4E:

$h_{fg}=1007.8Btu/lbm, s_{fg}=1.6529Btu/lbm.R$

Using the energy balance for the system:

$\dot E_{in}-\dot E_{out}=\bigtriangleup \dot E_{sys}=0\\\\\dot E_{in}=\dot E_{out}\\\\\dot Q_{in}+\dot m_{cw}h_1=\dot m_{cw}h_2\\\\\dot Q_{in}=\dot m_{cw}c_p(T_{out}-T_{in})\\\\\dot Q_{in}=44\times 1.0\times (73-60)=572\ Btu/s$

Hence, the rate of heat transfer in the heat exchanger is 572Btu/s

b. Heat gained by the water is equal to the heat lost by the condensing steam.

-The rate of steam condensation is expressed as:

$\dot m_{steam}=\frac{\dot Q}{h_{fg}}\\\\\dot m_{steam}=\frac{572}{1007.8}=0.5676lbm/s$

Entropy generation in the heat exchanger could be defined using the entropy balance on the system:

$\dot S_{in}-\dot S_{out}+\dot S_{gen}=\bigtriangleup \dot S_{sys}\\\\\dot m_1s_1+\dot m_3s_3-\dot m_2s_2-\dot m_4s_4+\dot S_{gen}=0\\\\\dot m_ws_1+\dot m_ss_3-\dot m_ws_2-\dot m_ss_4+\dot S_{gen}=0\\\\\dot S_{gen}=\dot m_w(s_2-s_1)+\dot m_s(s_4-s_3)\\\\\dot S_{gen}=\dot m c_p \ In(\frac{T_2}{T_1})-\dot m_ss_{fg}\\\\\\\dot S_{gen}=4.4\times 1.0\times \ In( {73+460)/(60+460)}-0.5676\times 1.6529\\\\=0.1483\ Btu/s.R$

Hence,the rate of entropy generation in the heat exchanger. is 0.1483Btu/s.R

4 0

4 years ago

A wave is produced from a vibrating string on a violin. Two observers are standing 20 m and 40 m away from the musician. The obs

max2010maxim [7]

Well the one that is closer can see and hear more

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3 years ago

A ball of moist clay falls 17.3 m to the ground. It is in contact with the ground for 24.0 ms before stopping. (a) What is the a

gizmo_the_mogwai [7]

Answer:

Acceleration, $767.08\ m/s^2$

Explanation:

Given that,

Height from a ball falls the ground, h = 17.3 m

It is in contact with the ground for 24.0 ms before stopping.

We need to find the average acceleration the ball during the time it is in contact with the ground.

Firstly, find the velocity when it reached the ground. So,

$v^2=u^2+2ah$

u = initial velocity=0 m/s

a = acceleration=g

$v=\sqrt{2gh} \\\\v=\sqrt{2\times 9.8\times 17.3} \\\\v=18.41\ m/s$

It is in negative direction, u = -18.41 m/s

Let a is average acceleration of the ball. Consider, v = and u = -18.41 m/s.

$a=\dfrac{v-u}{t}\\\\a=\dfrac{0-18.41}{24\times 10^{-3}}\\\\a=767.08\ m/s^2$

So, the average acceleration of the ball during the time it is in contact is $767.08\ m/s^2$ .

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3 years ago

Pls help ASAP. This is astronomy but there isn't an option :)

marin [14]

From largest to smallest they are: Universe, galaxy, solar system, star, planet, moon and asteroid.

Explanation:Let's describe them from smallest to largest. In fact the size order is not exact as there are exceptions.An asteroid is a rocky body which lies in the asteroid belt between Mars and Jupiter. They are typically quite small object. The largest asteroid Ceres has been reclassified as a dwarf planet.A moon is typically a rocky body which is in orbit around a planet. Some moons such as our Moon are quite large and are typically bigger than asteroid. Some moons can actually be smaller than some asteroids.A planet is a nearly spherical body which is in orbit around the Sun. Planets are larger than moons.A star is what planets orbit around. It is the source of light and heat. Our Sun is a star which is many times bigger than all of the planets.A solar system is a star and all of its planets, asteroids, comets and other bodies. It is significantly bigger than a star.A galaxy, such as our Milky Way Galaxy, is a collection of solar systems orbiting around a central core. Most galaxies have a supermassive black hole at their centres.Galaxies also form clusters which are large scale structures.The universe is everything. It contains billions of galaxies. Lots of information RIGHT!!!!

YOUR VERY WelCoMe!!!! :) :) :) :) :0 :)

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3 years ago

Why a plastic pen which is rubbed with hair,is able to attract small pieces of papers

AURORKA [14]

Answer:

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3 years ago