PE Mechanical: HVAC and Refrigeration
Connect psychrometric chart readings and equipment curves to the actual air path, energy boundary and system constraint.
Explore the original visual lessons and method cards below. Free candidate sign-in opens 28 saved exercises; paid enrollment remains closed. Twelve response-format drills per program cover numeric entry, select-two, matching and graphic regions.
Equipment → schematic → engineering decision
Conceptual equipment companion and exact process schematic. Use supplied case values for calculations.
Follow mixing, wet cooling and downstream reheat. Identify which component can actually remove water.
Existing equipment illustration paired with a new, precisely plotted USCS teaching curve. The linked narrated lesson uses its own stated SI example.
Parallel pumps share inlet and discharge head; total flow is the sum of pump flows.
Conceptual equipment companion and precise tower schematic. Use the individual exercise values, not values borrowed from another figure.
The tower receives evaporator load plus the compressor input that reaches the condenser, and any other explicitly included heat.
Conceptual equipment companion with an exact energy-boundary schematic. The room boundary determines the load.
Identify which electrical losses and shaft-work dissipation occur inside the conditioned room.
14.696 psia. This original orthogonal dry-bulb–humidity-ratio chart teaches the relationships; its geometry differs from the chart in your authorized reference. RH uses solid curves; other families use distinct line patterns.
Wet-bulb curves are calculated as thermodynamic wet bulb. They are close to, but distinct from, constant-enthalpy lines.
Original authored teaching material. Use your authorized examination references to rehearse the actual chart geometry, search headings and listed standards for your exam.
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Sign in and open the labCover the explanation and state the method in your own words. Revisit a card after a missed problem, then apply it to a fresh question.
Method 1
What crosses the chosen boundary? What stays inside?
Draw the room, plant, branch or construction quantity boundary. Name where every energy, mass or load contribution acts.
An indoor motor driving outdoor equipment contributes indoor losses, while exported shaft work dissipates elsewhere.
Method 2
Are these quantities comparable before you combine them?
Write units beside every input. Identify actual or standard airflow, dry-air or total mass, dry or moist soil and bank, loose or compacted volume.
Actual cfm requires specific volume at the actual measurement state. Standard cfm uses its explicitly defined reference density.
Method 3
Which requirement limits the proposed design?
Calculate independent capacity, safety or performance limits separately. Enforce all required lower and upper bounds.
Minimum coil area is the larger independent airflow or thermal requirement. Parallel route losses are compared rather than summed.
Method 4
What should the sign and approximate magnitude be?
Read chart labels and pressure first. Estimate before calculating. Preserve enough precision internally and report a justified result.
A chart reading is an estimate. Do not distinguish answers more finely than the plotted scale supports; numeric training tolerances are exercise-specific.
These original exercises have undergone internal technical and software checks. View the review scope, completed checks and remaining validation steps. Suggested working times are study guides.