22-Mec-B2 Environmental Control in Buildings, December 2019: worked solutions

Paper format. National Examinations, December 2019 — 16-Mec-B2 Environmental Control in Buildings. Three hours, open book: only textbooks and reference books are permitted (no notes and no solved problems), any non-communicating calculator is allowed, and candidates are expected to bring both an environmental-control text and steam tables because the tables and graphs in those books are needed. Eight problems are printed at 20 points each and only the first five in the exam book are graded, so the printed paper totals 160 points and a graded script totals 100. Psychrometric charts (IP and SI) and an R-134a pressure–enthalpy diagram are attached as the last three pages. All eight problems are worked below.

Reference texts for this subject.

ASHRAE Handbook — Fundamentals, Ch. 1 (Psychrometrics), Ch. 14 (Climatic Design Information), Ch. 16 (Ventilation and Infiltration), Ch. 19 (Energy Estimating and Modeling Methods), Ch. 21 (Duct Design).
McQuiston, Parker & Spitler, Heating, Ventilating and Air Conditioning: Analysis and Design, 6th ed. — plant psychrometry, duct design, infiltration and the degree-day method.
Jones, Air Conditioning Engineering, 5th ed. — percentage saturation, cooling-tower analysis, apparatus dew point and coil by-pass factor.
Çengel & Ghajar, Heat and Mass Transfer, 6th ed., Ch. 3 — one-dimensional composite walls and thermal bridging; Table A-5 for building-material conductivities.
Stoecker & Jones, Refrigeration and Air Conditioning, 2nd ed. — vapour-compression cycles and heat pumps; ASHRAE Refrigerant Tables for R-134a on the datum of the attached chart (h_f = s_f = 0 at −40 °F).
Eastop & McConkey, Applied Thermodynamics for Engineering Technologists, 5th ed. — the SI cooling-tower mass/energy balance in the form this paper uses.
Canadian context: ASHRAE Standard 170 Ventilation of Health Care Facilities (adopted by CSA Z317.2 for Canadian hospitals); Health Canada Residential Indoor Air Quality Guidelines; National Building Code of Canada 9.36 and the National Energy Code of Canada for Buildings (NECB 2020); Environment and Climate Change Canada Canadian Climate Normals for degree-day and design-temperature data.

Check — assumptions declared under cover-page instruction 1

Cover-page instruction 1 asks candidates to state any interpretive assumption with the answer. Four are needed on this paper and each is flagged again where it is used: the operating-room dry-bulb temperature in Problem 1 (not given — taken as 75 °F, the top of the ASHRAE 170 range, because it is the only part of that range that also satisfies the 60 % relative-humidity ceiling); the Winnipeg design conditions and degree-day base in Problem 6 (the paper says “select the design conditions”); the indoor design temperature and neutral pressure level in Problem 7(b); and the duct roughness and fitting allowance in Problem 8. Everything else in the paper is fully determined by the data given.

22-Mec-B2 Environmental Control in Buildings: December 2019