Blank is an art form in which the focus is to make life and society better

Refrigerant 134a at p1 = 30 lbf/in2, T1 = 40oF enters a compressor operating at steady state with a mass flow rate of 200 lb/h a

Mazyrski [523]

Answer:

a) $\mathbf{Q_c = -3730.8684 \ Btu/hr}$

b) $\mathbf{\sigma _c = 4.3067 \ Btu/hr ^0R}$

Explanation:

From the properties of Super-heated Refrigerant 134a Vapor at $T_1 = 40^0 F$ , $P_1 = 30 \ lbf/in^2$ ; we obtain the following properties for specific enthalpy and specific entropy.

So; specific enthalpy $h_1 = 109.12 \ Btu/lb$

specific entropy $s_1 = 0.2315 \ Btu/lb.^0R$

Also; from the properties of saturated Refrigerant 134 a vapor (liquid - vapor). pressure table at $P_2 = 160 \ lbf/in^2$ ; we obtain the following properties:

$h_2 = 115.91 \ Btu/lb\\\\ s_2 = 0.2157 \ Btu/lb.^0R$

Given that the power input to the compressor is 2 hp;

Then converting to Btu/hr ;we known that since 1 hp = 2544.4342 Btu/hr

2 hp = 2 × 2544.4342 Btu/hr

2 hp = 5088.8684 Btu/hr

The steady state energy for a compressor can be expressed by the formula:

$0 = Q_c -W_c+m((h_1-h_e) + \dfrac{v_i^2-v_e^2}{2}+g(\bar \omega_i - \bar \omega_e)$

By neglecting kinetic and potential energy effects; we have:

$0 = Q_c -W_c+m(h_1-h_2) \\ \\ Q_c = -W_c+m(h_2-h_1)$

$Q_c = -5088.8684 \ Btu/hr +200 \ lb/hr( 115.91 -109.12) Btu/lb \\ \\$

$\mathbf{Q_c = -3730.8684 \ Btu/hr}$

b) To determine the entropy generation; we employ the formula:

$\dfrac{dS}{dt} =\dfrac{Qc}{T}+ m( s_1 -s_2) + \sigma _c$

In a steady state condition $\dfrac{dS}{dt} =0$

Hence;

$0=\dfrac{Qc}{T}+ m( s_1 -s_2) + \sigma _c$

$\sigma _c = m( s_1 -s_2) - \dfrac{Qc}{T}$

$\sigma _c = [200 \ lb/hr (0.2157 -0.2315) \ Btu/lb .^0R - \dfrac{(-3730.8684 \ Btu/hr)}{(40^0 + 459.67^0)^0R}]$

$\sigma _c = [(-3.16 ) \ Btu/hr .^0R + (7.4667 ) Btu/hr ^0R}]$

$\mathbf{\sigma _c = 4.3067 \ Btu/hr ^0R}$

5 0

3 years ago

Is a water proof material used around tubs and

Leviafan [203]

I think it’s hard board

4 0

3 years ago

Read 2 more answers

In addition to bandages and gauze, it's recommended that a first aid kit also contain ___________.

gavmur [86]

D scissors or tweezers because in the medical field the EMR will likely need to use the tool for the patients like ripping a clothing

3 0

3 years ago

Read 2 more answers

An electric winch operates on 140 volts [V] and draws 6 amperes [A] of current. The winch has an efficiency of 64%. The winch

Elis [28]

Answer:

Explanation:

efficiency = (energy output / energy input)

energy input = ivt where i is current = 6 A, v is volts = 140 and t time = 11 seconds

energy input = 6 × 140 × 11 = 9240 J

energy output = 0.64 × 9240 = 5913.6 J

510 pound-force = 2268.593 N

at height h, potential energy = mgh = 5913.6 J

2268.593 × h = 5913.6

h = 5913.6 / ( 2268.593) = 2.61 m

3 0

3 years ago

A 3.7 g mass is released from rest at C which has a height of 1.1 m above the base of a loop-the-loop and a radius of 0.2 m . Th

Dmitrij [34]

Answer:

Normal force = 0.326N

Explanation:

Given that:

mass released from rest at C = 3.7 g = 3.7 × 10⁻³ kg

height of the mass = 1.1 m

radius = 0.2 m

acceleration due to gravity = 9.8 m/s²

We are to determine the normal force pressing on the track at A.

To to that;

Let consider the conservation of energy relation; which says:

mgh = mgr + 1/2 mv²

gh = gr + 1/2 v²

gh - gr = 1/2v²

g(h-r) = 1/2v²

v² = 2g(h-r)

However; the normal force will result to a centripetal force; as such, using the relation

N =mv²/r

replacing the value for v² = 2g(h-r) in the above relation; we have:

Normal force = 2mg(h-r)/r

Normal force = 2 × 3.7 × 10⁻³ × 9.8 ( 1.1 - 0.2 )/ 0.2

Normal force = 0.065268/0.2

Normal force = 0.32634 N

Normal force = 0.326N

6 0

3 years ago