Mec-A1 — Applied Thermodynamics and Heat Transfer
Thermodynamics: Review of the fundamental laws of thermodynamics, introductory psychrometry and analysis of the ideal gas compressor cycle, Rankine cycle, Otto cycle, Diesel cycle, Brayton cycle and the vapour compression refrigeration cycle. Heat Transfer: Application of the principles of steady and transient conduction heat transfer, natural and forced convection heat transfer and radiation heat transfer. Thermal analysis of heat exchangers.
Subject outline
Mec-A1 Applied Thermodynamics and Heat Transfer is a Mechanical Engineering technical exam (PEO National Examination 16-Mec-A1) set in two halves. Part A is thermodynamics: the first law for a closed system with a non-ideal equation of state; throttling, quality and the property tables for ammonia, R-134a, Freon-12 and steam; a two-stage steam turbine with reheat, its reheat fraction and its isentropic efficiency; two gas turbines with an intermediate heat exchanger; a flash chamber feeding a turbine; charging a refrigeration unit with Freon-12; the power of a reciprocating air compressor; irreversible adiabatic compression and the entropy it generates; and vapour-compression refrigeration and heat pumps, actual against ideal, with COP and running cost. Part B is heat transfer: a composite wall and the minimum thickness that holds its outer face at a set temperature; radial conduction through a thick-walled tube with and without an added layer; internal heat generation in a current-carrying conductor; an evaporator submerged in an ice–water tank; combined natural convection and radiation from a vertical plate, solved by iteration; lumped-capacitance cooling of a molten droplet; and heat exchangers by both the LMTD and the effectiveness–NTU methods.
The paper is 3 hours and open book: the front page says candidates may make use of any textbooks, references or notes, and expects each candidate to bring both a thermodynamics text and a heat transfer text for the tables and graphs they contain. Any non-communicating calculator is permitted, and its make and model must be written inside the cover of the first answer book. Each sitting sets eight questions, Q1 to Q4 in Part A (Thermodynamics) and Q5 to Q8 in Part B (Heat Transfer), and a complete examination is the answers to five of them: either three from Part A and two from Part B, or two from Part A and three from Part B. Mark on the cover which answers you want graded — otherwise they are graded in the order written, up to three per section — and note that every question carries the same value, with no mark split printed inside a question. May 2019 and December 2019 print the same seven notes word for word, so the rubric above is both sittings.
What this course gives you
Worked solutions — May 2019 and December 2019 in full: eighteen worked solutions, because Q1 of each paper is two independent problems, (a) and (b), and the pack solves them as two. Every step of the hand-written working is retypeset as real text and live maths, the final answers are pulled out into a box at the head of each question, and the steam, ammonia, R-134a and Freon-12 table extracts are reproduced beside the values read from them. Every published number has been recomputed, and where the arithmetic does not follow from the line above it the step carries a flagged correction of its own — headed, and set into the working at the exact point that goes wrong — showing the value the same numbers actually give. There are eleven such flagged steps across the two sittings, seven on May 2019 and four on December 2019, and the published figure is always shown too, so nothing has been silently overwritten. The largest: December Q7's Nusselt number for the cooling weld droplet is printed as 6.56 when the Whitaker correlation the solution itself prints, with its own Re = 31.64, Pr = 0.729 and viscosity ratio 0.445, gives 4.05 — so h is 208 W/m²K rather than 337, and 198 W/m²K once the viscosity ratio is taken at the 1700 K surface as Whitaker specifies — and two lines later a division that gives 2940 K/s is printed as 3382.8; the corrected cooling rate is about 1934 K/s. Among the rest: May Q2's reheat fraction ξ = 0.3608 does not balance the 7500 kW the question states (it gives 7515), and the pack's own enthalpies make it 0.3551; May Q2(c) takes the turbines' actual work as h₁ − h₅, which leaves out the reheat, so its 90.4% is not the two-stage efficiency — stage by stage it is about 96%; May Q1(b) substitutes h₁ = 421 for the 421.7 kJ/kg found two lines earlier, so the quality after the valve is 0.1867 rather than 0.1862; May Q7 evaluates a Grashof number with L⁴ in place of L³; May Q8 sizes the tube bank with 920 kg/m³, the density of ice carried over from Q6, where the question states 961, which changes the count from 38 tubes to 36, and it halves the single-pass length without the two-pass correction factor F = 0.877, so each pass needs 1.70 m, not 1.408 m; May Q4 reads s₁ = 0.9609 where its own table gives 0.9606, so the compressor's isentropic efficiency is 91.8%, not 92.07%; December Q1(b)(iv) treats the charging of the evacuated unit as cooling at a fixed 0.6 MPa to a compressed liquid, where the 5 kg actually ends as the liquid–vapour mixture of part (iii), so the heat removed is 548 kJ, not 736.48 kJ; and December Q4's daily-saving line is out by a factor of ten with the subtraction the wrong way round. Seven further headed notes clear up a label, a unit or a rounded intermediate — a 4.63 J that is exactly 4.75 J in May Q1(a), a COP written 3.81 where the same numbers gave 3.85 in May Q4 — without changing a conclusion. Study notes — ten condensed topics: the fundamental laws of thermodynamics; ideal-gas laws and psychrometry; thermodynamic cycles in overview; the Rankine cycle in detail; the Otto and Diesel cycles in detail; the Brayton cycle and vapour-compression refrigeration; an introduction to heat transfer; steady and transient conduction; natural and forced convection; and the thermal analysis of heat exchangers — fully typeset, with 43 figures drawn for them, most of them around the very questions the two papers set. Freon-12 property data — the saturated liquid–vapour table and the two superheated-vapour interpolation tables the author built for December Q1(b) and Q4, reproduced as live tables so every value read in those two solutions can be checked without leaving the page. Formula sheet — two pages in five groups: laws, work and heat; ideal gas; vapours and mixtures; cycles and efficiency; and heat transfer. This exam is open book, so print it, check it against your own text and take it in. Exam stationery — four blank templates to print: a ruled answer sheet matching the answer-book layout, dot-grid rough-work paper, graph paper and isometric paper. All of it may be carried into the exam. Practice papers — the two question papers on their own, unmarked, for a timed run: May 2019 (9 pages, including the ammonia and R-134a property tables) and December 2019 (6 pages, Part A and Part B) — the same two sittings that are solved above, to sit cold and mark yourself against the final-answer boxes. Reference links — ten YouTube topic searches, each with a note on what it is good for: lecture series on the laws, entropy and cycles; heat transfer from first principles; Rankine, Otto, Diesel and Brayton walked through on T–s diagrams; worked problem sets in the style of the paper; LMTD and effectiveness–NTU on real exchangers; convection correlations and when each applies; the Carnot benchmark; and MIT OpenCourseWare thermodynamics.
Throughout, 77 figures were drawn for this pack — 34 in the solutions and 43 in the notes — alongside 18 crops kept from the question papers and the original hand-written solutions (the T–s and p–v sketches, the system diagrams and the two design charts, in colour because the colour coding carries meaning), so the reheat cycle sits on a real water saturation dome with the pack's own entropies, the oven window shows its 500 / 219 / 50 / 25 °C profile, the heated tube its radial profile before and after insulating, and the two-shell-pass effectiveness chart is computed rather than copied.