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3 years ago

10

Why is it important to have knowledge on abbreviations, sign and symbols in masonry servicing job in the construction business s

ector?

1 answer:

marta [7]3 years ago

5 0

Maybe To know short cuts on the long run. And it is a way of coding

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Air at 40C flows over a 2 m long flat plate with a free stream velocity of 7 m/s. Assume the width of the plate (into the paper)

mezya [45]

Complete Question

Air at 40C flows over a 2 m long flat plate with a free stream velocity of 7m/s. Assume the width of the plate (into the paper) is 0.5 m. If the plate is at a co temperature of 100C,find:

The total heat transfer rate from the plate to the air

Answer:

$q=1.7845$

Explanation:

From the question we are told that:

Air Temperature $T_1=40c$

Length $l=2m$

Velocity $v=7m/s$

Width $w=0.5$

Constant temperature $T_t= 100C$

Generally the equation for Total heat Transfer is mathematically given by

$q=hA(T_s-T_\infty)$

Where

h=Convective heat transfer coefficient

$h=29.9075w/m^2k$

Therefore

$q=h(L*B)(T_s-T_\infty)$

$q=29.9075*(2*0.5)(100+273-(40+273))$

$q=1794.45w$

$q=1.7845$

5 0

3 years ago

Errors in the output voltage of an actual integrated circuit operational amplifier can be caused by : Select one:

natta225 [31]

Answer:

Option B

Explanation:

An operational amplifier usually has a high open loop gain of around 10^5 which allows a wide range get of feed back levels in order to achieve the desired performance so therefore a low open loop gain reduces the range feed back level thereby reducing the performance which can cause errors in the output voltage.

7 0

3 years ago

What is a ton of refrigeration?

AURORKA [14]

Explanation:

The unit refrigeration is generally is given in terms of tons.In refrigeration compressor consume some amount of work to produce the cooling effect with the help of evaporator and condenser.

In the simple words ton is the cooling load of refrigeration system.

So

1 ton = 3.5 KW

1 ton = 12,000 BTU/hr

6 0

3 years ago

Identify factors that can cause a process to become out of control. Give several examples of such factors.

Oliga [24]

Answer:

Explained

Explanation:

This situation can occur because of various factors such as:

Gradual deterioration of lubrication and coolant.
change of environmental condition such as temperature, humidity, moisture, etc.
Change in the properties of incoming raw material
An increase or decrease in the temperature of the heat treating operation
Debris interfering with the manufacturing process.

4 0

3 years ago

The hot and cold inlet temperatures to a concentric tube heat exchanger are Th,i = 200°C, Tc,i = 100°C, respectively. The outlet

alexgriva [62]

Answer:Counter,

0.799,

1.921

Explanation:

Given data

$T_{h_i}=200^{\circ}C$

$T_{h_o}=120^{\circ}C$

$T_{c_i}=100^{\circ}C$

$T_{c_o}=125^{\circ}C$

Since outlet temperature of cold liquid is greater than hot fluid outlet temperature therefore it is counter flow heat exchanger

Equating Heat exchange

$m_hc_{ph}\left [ T_{h_i}-T_{h_o}\right ]=m_cc_{pc}\left [ T_{c_o}-T_{c_i}\right ]$

$\frac{m_hc_{ph}}{m_cc_{pc}}$ = $\frac{125-100}{200-120}=\frac{25}{80}=C\left ( capacity rate ratio\right )$

we can see that heat capacity of hot fluid is minimum

Also from energy balance

$Q=UA\Delta T_m=\left ( mc_p\right )_{h}\left ( T_{h_i}-T_{h_o}\right )$

$NTU=\frac{UA}{\left ( mc_p\right )_{h}}$ = $\frac{\left ( T_{h_i}-T_{h_o}\right )}{T_m}$

$T_m=\frac{\left ( 200-125\right )-\left ( 120-100\right )}{\ln \frac{75}{20}}$

$T_m=41.63^{\circ}C$

NTU=1.921

$And\ effectiveness \epsilon =\frac{1-exp\left ( -NTU\left ( 1-c\right )\right )}{1-c\left ( -NTU\left ( 1-c\right )\right )}$

$\epsilon =\frac{1-exp\left ( -1.921\left ( 1-0.3125\right )\right )}{1-0.3125exp\left ( -1.921\left ( 1-0.3125\right )\right )}$

$\epsilon =\frac{1-exp\left ( -1.32068\right )}{1-0.3125exp\left ( -1.32068\right )}$

$\epsilon =\frac{1-0.2669}{1-0.0834}$

$\epsilon =0.799$

5 0

3 years ago