Module 2 - Assessment 1

Which thermodynamic law talks about energy degradation?

Second law

Which of the following statement is incorrect regarding moist air (mixture of water vapor and dry air)?

Moist air pressure can be taken as equal to the pressure of dry air

What is the heat transfer mechanism applicable for opaque solids?

Heat conduction

Which of the following statement is incorrect about psychrometric chart?

A horizontal process line indicates that the relative humidity remains constant

Cooling of meat, fruits and vegetables are examples of heat transmission by:

Transient Convection

Which of the following energy form is a path function?

Work

What happens during sensible heating process?

Temperature increases and relative humidity decreases

Determine the amount of fuel to be used to evaporate 280 lbm of moisture from a product if the thermal efficiency in drying is 30%, net heating value of fuel is 19,200 Btu/lbm and the latent heat of vaporization of water within the product of 120°F is 1,151 Btu/lbm.

56 lbm

It is the heat added or removed from a substance causing a change in its state without changing its temperature.

Latent heat

What is the quality of 20 kg R-134a at 2°C contained in a 1-m3 tank if the specific volume of saturated liquid and vapor are 0.0007761 m3/kg and 0.064690 m3/kg, respectively?

77.02%

When a system deviates infinitesimally from equilibrium at every instant of its state, it is undergoing

Quasi-steady process

Which process appears as horizontal lines on the psychrometric chart?

Sensible heating and cooling

A thermodynamic process in which the system’s properties do not change.

Steady-state process

The energy requirement for size reduction is a function of a common dimension of the material.

Kick’s Law

It is the conversion of sugar in plant tissues to carbon dioxide, water, and oxygen gas.

Respiration

Select the incorrect statement about the dew-point temperature of the moist air.

It cannot be below the dry-bulb temperature

A rigid container equipped with a stirring device contains 2.5 kg of oil. Determine the net increase in the internal energy when 0.4 kJ/kg heat is transferred to the oil 0.6 kJ/kg is applied to the stirring device.

2.5 kJ

A type of process in which energy interaction brought about by the difference in temperature is not possible or can be neglected.

Adiabatic

The basis in classifying flow regime in forced convection.

Reynolds number

What method of heat exchanger analysis is to be used when selecting a heat exchanger that will achieve a specified temperature change in a fluid stream of known mass flow rate?

LMTD method

Which law that states that the rate of heat transfer across any plane normal to the direction of heat flow is proportional to the wall area and temperature gradient in that direction?

Fourier’s law

The maximum rate of radiation that can be emitted from a surface is called

Blackbody radiation

Radiation heat exchange between surfaces depends on the orientation of the surfaces relative to each other, and this dependence is accounted for by the

View factor

For an ideal gas, the change in internal energy is related to what property?

c_v

100 kg of lean beef is to be cooled from 18 to 4°C, then frozen and cooled to -18°C (Assume freezing point to at -2°C). The moisture content is 69.5%, so the latent heat is estimated to be 233 kJ/kg. If the specific heat of beef before and after freezing are 3.52 kJ/kg-K and 2.12 kJ/kg-K, respectively, estimate the cooling load.

33.7 MJ

What is the heat loss per ft2 of a 9-inch-thick brick-kiln wall made of a material with thermal conductivity of 0.18 BTU/hr-ft-°F? The outside and inside temperature are 1500°F and 400°F, respectively.

264 BTU/hr-ft2

Compute the amount of heat needed to drop the temperature of 100 cans, each containing 250 mL of milk, from 32°C to 25°C. Assume a specific weight of milk equal to 0.99 kg/L. The specific heat of milk is 0.93 Btu/lbm-°F.

641 Btu

Which of the following is incorrect statement about water activity?

Decreases with increasing moisture content

If 35,000 kg of whole milk containing 4% fat is to be separated in a 6-hour period into skim milk with 0.45% and cream with 45%, what is the flow rate of cream from a continuous centrifuge which accomplishes this separation?

465 kg/hr

What is the ideal thermodynamic cycle for spark-ignition ICE?

Otto cycle

A solar dryer is used to reduce the moisture content of four tons of paddy rice from 25% to 15% wet basis. The amount of moisture removed is about

471 kg

An air-conditioned room is maintained at 24 degree C while the outside air temperature is 32 degree C. What is the temperature difference in degrees Fahrenheit?

14.4

A pressure of 1.5 inch of water is required to move air up through a bin of grain at 20 cfm per sq. ft. of floor area. If the floor area is 175 sq. ft., what fan horsepower is required assuming 75% efficiency?

1.107 hp

At an average temperature of 100°C, hot air flows through a 2.5 m long tube with an inside diameter of 50 mm. The temperature of the tube is 20°C along its length. Convective heat transfer coefficient is 20.1 W/m2-K. Determine the heat transfer from air to tube.

632 W

Shrimp harvested in a pond situated in Bohol are packed in insulated sheet metal containers and mixed with crushed ice while in transit to the shrimp processing plant in Manila. Initial temperature of the product is about 25°C and it is desired to cool the shrimp at approximately 0°C during shipment. Estimate the product load, in kJ/kg. For shrimp highest freezing temperature is -2.2°C, Cp above freezing is 3.38 kJ/kg-K, Cp below freezing is 1.79 kJ/kg-K, and latent heat of fusion is 254 kJ/kg.

84.5

A rice miller buys 100 kg of dried and clean palay at ₱13/kg. assuming that his cost of operation is ₱4/kg milled rice, how much should he sell, in ₱/kg, to break even. Neglect by-products and assume milling recovery of 64%.

24.3

Determine the horsepower requirement of a cyclone operator for cleaning the air coming from the LSU dryer if the blower capacity is 8000 cfm and static pressure at the exhaust of the dryer is 3 in. water. Dryer capacity is 3 tons/hr.

3.89 hp

What is the ideal thermodynamic cycle for gas turbine power plant operating in a close cycle?

Brayton cycle

A piston cylinder initially contains 0.4 m3 air at 100 kPa and 80°C. The air is then compressed to 0.1 m3 in such a way that the temperature inside the cylinder remains constant. Determine the work done during the process.

-55.4 kJ

How many kilograms of rice hulls are needed to dry 1.5 tons of palay from 24% to 14% MC w.b.? Assume latent heat of vaporization is 2,500 kJ/kg, heating value of rice hull is 14 MJ/kg and efficiency of 97%.

32.11 kg

The heat conduction equation is analogous to electric current flow, in which the temperature difference is analogous to_________.

Voltage difference

An engineer in an electric-generation station claims that the plant is 80% efficient. During your inspection, the flames in the boiler reach a temperature of 920°C and the cooling water coming from the nearby river measures 27°C. Is the engineer’s claim

Invalid

The throttling process in a throttling valve or expansion valve of a refrigeration system is

Isenthalpic

Consider a spherical ball at 800 K suspended in air. Assuming the ball closely approximates a blackbody, determine the total blackbody emissive power.

23.2 kW/m2

Estimate the product cooling load of refrigerating 0.25 tons of shrimp initially at 27°C to -18°C. Freezing point of shrimp is -2.2°C and the specific heat above and below freezing are 3.65 kJ/kg-°C and 2.16 kJ/kg-°C, respectively.

35.18 MJ

Which of the following is/are true about ideal gases?

i. Has very high temperature with respect to the critical temperature

ii. Has very high pressure with respect to the critical pressure

iii. Pressure is directly proportional to absolute temperature at constant volume

iv. Volume is directly proportional to pressure at constant temperature

v. Absolute temperature is directly proportional to volume at constant pressure

i, iii, & v

Determine the capacity of a horizontal steel conveyor to convey paddy rice (density = 36 lbm/ft3) if the flight length is 12 in., flight height is 0.4 of the flight length, and flight speed is 100 ft/min.

39.19 tons/hr

What is the highest theoretical coefficient of performance of a refrigerator if the temperature inside the refrigerator is -5°C and the temperature of the surrounding air is 27°C?

8.38

Which of the following statement is incorrect about drying?

a. Isenthalpic process

b. Will result in the decrease of the humidity ratio of the drying air

c. Will result in the increase of the relative humidity of the drying air

d. Involves both heat and mass transfer

b. Will result in the decrease of the humidity ratio of the drying air

This dimensionless number represents the enhancement of heat transfer through a fluid layer as a result of convection relative to conduction across the same fluid layer.

Nusselt number

What is the primary function of an electric motor in agricultural applications?

Convert electrical energy to mechanical energy

A farmer needs a motor for continuous operation of an irrigation pump. Which type of motor duty rating is most appropriate?

Continuous Duty

A grain mill requires a motor with high starting torque. Which type of motor would be most suitable?

Capacitor-start induction motor

A 3-horsepower motor is to be replaced with an equivalent electric motor. What is the recommended electric motor rating following standard conversion?

3 hp

What factor must be considered when selecting a motor to replace an internal combustion engine in an agricultural machine?

The electric motor should have approximately 2/3 the power rating of the engine

A person is asked to pump water for irrigation continuously for 4 hours. what is the estimated power output?

0.13 hp

farmer is choosing a harness for his draft oxen. Which type of harness is best suited for bovines?

Yoke

A draft animal supplies useful power by exerting a pull at a certain speed. What factor does NOT directly influence the pull exerted by the animal?

Color of the animal’s harness

A village cooperative is considering using water buffalo for plowing instead of tractors. What is one of the main reasons for this decision?

Lower operational cost

What is the primary reason why farmers in developing countries still rely on human and animal power?

Limited access to mechanized farming equipment

A farmer is selecting transport equipment for his draft animals. Which option allows for the highest load capacity?

Cart

A small-scale farmer needs to irrigate crops but has no access to an engine-powered pump. Which of the following would be a practical solution?

Using a treadle pump

A farmer is using an ox-drawn plow for land preparation. What is the expected depth of plowing?

15–18 cm

According to PAES 109: 2000, the handle bar of the walking-type tractor should be made of:

Black Iron (BI) pipe (schedule 40)

The minimum peak transmission efficiency of the walking-type tractor must be:

85%

Which of the following is required for operator safety on the walking-type tractor?

Belt guard or cover

What is the maximum allowable noise level emitted by the walking-type tractor, measured 50 mm from the operator’s ear?

92 dB (A)

Which of the following is a secondary tillage operation?

Harrowing

What is the primary function of a moldboard plow?

To invert the soil

Which tillage implement is used to break up compacted soil at greater depths?

Chisel plow

What is the term for the distance between the outermost edges of a tillage implement?

Implement width

Which tillage system aims to maintain a minimum of 30% residue cover on the soil surface?

Conservation tillage

What is the name of the soil-handling implement that forms uniform ridges for planting?

Lister

Which tillage tool is primarily used for cutting and turning a furrow slice?

Moldboard

What is the term for the soil mass cut, lifted, pulverized, inverted, and thrown to one side of the bottom plow?

Furrow slice

Which tillage implement is used for shallow post-plant tillage to loosen the soil and eradicate weeds?

Cultivator

The Philippine standard for rice combine harvester specifications.

PNS/PAES 224:2015

When a machine is driven directly from the shaft of a power source, the power is transmitted using:

Direct drive

A gang arrangement in which the harrow is not centrally located with respect to the tractor position.

Offset

Theoretical air-to-fuel ratio of Propane (mass method).

15.6

What is the specific fuel consumption of an engine that has a brake thermal efficiency of 21.20%? The fuel contains 20,000 BTU/lb.

0.6 lb/hp-hr

The value of the theoretical maximum efficiency of a wind turbine or the maximum proportion of wind energy that can be converted into mechanical energy by a turbine, also known as Betz coefficient.

16/27

Engr. Pelenio needed 5 pcs of work benches for his business. He found out that he needed 10 pcs of 2”x3”x12’ and 6 pcs of 2”x2”x6’ for each work bench. How many board feet of lumber would he need in total?

360 bd-ft

If a sprocket is used for a chain, a sheave is used for:

V-belt

Engr. Lomigo wants to eradicate mango fruit flies that are causing damages to his mango farm. Which type of sprayer would be the most suitable for efficient and effective pest control.

Power sprayer

Which level of government is responsible for maintaining national database of all registered agricultural and fishery machinery?

BAFE

It is the ratio of the drawbar power and the wheel axle power.

Traction Efficiency

A corn sheller cylinder will be driven by 10-hp diesel engine through V-belt. The engine has a speed of 1800 rpm while the required speed of the corn sheller is 650 rpm. The effective diameter of the driver pulley is 12 inches. What should be the diameter of the driven pulley?

33 in

It is the ratio between the number of weeds removed by the weeder to the number of weeds present per unit area.

Weeding index

The draft of implement in terms of force per unit area of tilled cross-section.

Specific Draft

It is the ratio between the mass of fuel consumed per unit of time and the corresponding measured power.

Specific Fuel Consumption

In an ideal Diesel engine, the combustion of fuel occurs at:

Constant pressure

Amount of power that the manufacturer specified for an engine.

Rated Power

Determine the seeding rate of an 8-rows ground seeder having a 25-cm row spacing if the ground wheel diameter is 80-cm? During the calibration test, the collected discharge is 450 grams for 10 revolutions of ground wheel.

89.5 kg/ha

If you need to penetrate deep into the soil to break up compacted layers, which implement would you use?

Subsoiler

Which cultivator is best suited for stony, uneven fields and light tillage?

Spring-Loaded Cultivator

Spring-Loaded Cultivator

Rigid-Tine Cultivator

If you need to prepare a fine seedbed for shallow-rooted weeds, which cultivator is the best choice?

Duckfoot Cultivator

For thorough soil mixing and pulverization, especially in heavy soils, which cultivator is ideal?

Rotary Cultivator

If you want to loosen compacted soils and improve aeration, which cultivator is recommended?

Chisel Cultivator