# MHR Sample Exam

### Mechanical Engineering HVAC & Refrigeration PE Sample Exam

Working through sample PE Exam questions is one of the most efficient methods of preparing for exam.

• Spend time understanding the intent of the question (i.e. what is the question writer actually testing you on)
• Find useful resources that help answer the questions in the Sample Exam (and similar questions)
• Assemble your resources into a system that you can use on exam day

If there is anything I can do for you as you work through this Mechanical Engineering HVAC & Refrigeration PE Sample Exam and as you prepare for the PE Exam, please do not hesitate to ask.

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MHR 01       Principles/Basic Engineering Practice/Economic Analysis:

An existing 100 hp condenser water pump can be upgraded at a cost of $9,000 and the annual maintenance costs will be$2,500. Or the owner can purchase a new, high-efficiency, 75 hp pump for $30,000 with annual maintenance costs of$1,000 to replace the existing pump. If the pumps both run 24 hours a day, 365 days a year and utility costs are \$0.12/kwh, which pump costs less (including maintenance) and what is the savings based on 1 year’s operation?

MHR 02       Principles/Basic Engineering Practice/Electrical Concepts:

A 460-volt, 3-phase feeder consisting of three #2/0 AWG wires is supplying a 90 KW load. If the load is balanced and the power factor is 70% lagging, what is the current per phase?

MHR 03       Principles/Thermodynamics/Cycles:

In a simple thermodynamic refrigerant cycle, what state is the refrigerant in between the condenser and the thermostatic expansion valve?

MHR 04       Principles/Thermodynamics/Properties:

Thermodynamic properties are divided into two types – intensive and extensive. An extensive property depends on size or extent of the system. Intensive properties exist an any point in space. Which of the following are categorized as intensive properties: (I) Pressure, (II) Temperature, (III) Volume, (IV) Density

MHR 05       Principles/Thermodynamics/Compression Processes:

Thermodynamic compression where no heat is transferred in or out is called ___________ compression.

MHR 06       Principles/Psychrometrics/Heating/Cooling Processes:

In psychrometrics, Humidity Ratio is defined as ________________ and sometimes called _______________:

MHR 07       Principles/Heat Transfer:

Determine the minimum insulation thickness required for a 6” hot water pipe (160°F). The maximum temperature on the outer surface of the insulation can be 100°F. Thermal conductivity of the insulation is 0.25 BTU-in./(hr-ft2-°F). The maximum heat loss from the pipe/insulation is 150 BTUh/ft.

MHR 08       Principles/Fluid Mechanics:

Compressible flow is generally related to fluids that have significant changes in density and Mach numbers higher than 0.3. Which of the following would not be considered a compressible flow?

MHR 09       Principles/Fluid Mechanics:

Using the Darcy-Weisbach equation, calculate the head loss in a 10 ft section of 3” pipe. The Moody friction factor is 0.075, the density of the fluid is 1 lb/ft3, and the velocity of the fluid is 4 ft/sec.

MHR 10       Principles/Energy Balances:

What is the discharge velocity of a 2” pipe discharging water into a reservoir? The water is traveling at 3 ft/sec inside the pipe at 60psi pressure. Assume no change in elevation.

A retail building 100’-0” wide by 200’-0” deep x 16’-0” high has the following characteristics:
1. the 2 sides and the rear of the building have an overall U-value of 0.11 BTU/ft2-hr-°F
2. the front of the building is constructed entirely of storefront glass panels with an overall U-value of 0.51 BTU/ft2-hr-°F
3. the roof has an overall U-value of 0.08 BTU/ft2-hr-°F
4. 75% of the overall floor space is to be used for occupancy and lighting calculations (sales area)
5. the occupancy loading is 66.67 sq. ft per person in the sales area
6. people sensible load is 250 Btuh/person
7. the outside air ventilation requirements are:

5 cfm per person
12 cfm per sq.ft. (sales area)
06 cfm per sq.ft. (warehouse area)

8. the lighting load is 3 watts per square foot
9. the overall miscellaneous power is 1 watt per square foot
10. the store is to be maintained at 75°F/50%RH
11. the design day is 97°F/75°F
12. the blow through air handling unit discharge temperature is 56°F and the fan motor heat is 1°F

The total air conditioning load in tons is most nearly? (neglect solar heat gain)

MHR 12       Applications/Equipment and Components/Cooling/Heating Coils:

An air handling unit cooling coil has the following characteristics: 7,500 cfm, 75°F/50%RH entering air temperature, 55°F/90%RH leaving air temperature, 42°F supply chilled water temperature, 52°F return chilled water temperature

Using the Water Vapor in Air chart provided, what gpm of chilled water is required?

MHR 13       Applications/Equipment and Components/Refrigeration Components:

In a simple refrigerant system, what is the order of equipment starting with the outdoor unit?

MHR 14       Applications/Equipment and Components/Refrigeration Components:

In a direct-expansion air conditioning system, what is the purpose of the refrigerant air dryer?

MHR 15       Applications/Systems and Components/Air Distribution:

What is the minimum duct insulation U-value dictated by ANSI/ASHRAE 90.1 for supply ductwork routed in a ventilated attic in climatic zone 4? The ductwork is connected to a heat-pump air-conditioning unit.

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The Mechanical Engineering HVAC & Refrigeration PE Sample Exam is designed to help you prepare for the PE Exam by following these 3 steps:

1. Work through the information in the Sample Exam … follow the references … dig deep.
• following the references/links for the problems will expand your knowledge of the subject.
2. Work as many problems as you can find and note where you have difficulties.
• working the problems in the Sample Exam plus any additional examples you can find is an excellent test preparation method.
3. Take the time to put together a comprehensive Test-Day Resource Library©
• the Test-Day Resource Library© is my #1 recommendation for everyone preparing for the PE Exam.

Remember, this is a process. If you will:

• spend time every day gathering information
• work the example problems in the Mechanical Engineering HVAC & Refrigeration PE Sample Exam
• assemble the resources into an organized system

… you will be successful.