Module Title: Building Services Mechanical 2

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1 CORK INSTITUTE OF TECHNOLOGY INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ Semester 1 Examinations 2008/09 Module Title: Building Services Mechanical 2 Module Code: MANU6008 School: Mechanical and Process Engineering. Programme Title: Bachelor of Engineering in Building Services Engineering Year 2 Programme Code: EBSEN_7_Y2 External Examiner(s): Internal Examiner(s): Mr. Paul O Sullivan, Dr. Mervyn Smyth Mr. Willie Bateman Instructions: Answer any 3 questions. All questions carry equal marks. Duration: 2 hours. Sitting: Winter 2008 Requirements for this examination: Attachments to be provided, for student reference, with this exam paper. Q1d. Tables 1, 2, 3 and 4 Hot and Cold water pipe work design. Table C4.18 Page C4-40 Flow of Water at 10 0 C in Copper Pipe. Hot and Cold Water design spreadsheet. Q2d CIBSE Tables A3.8 (Rsi), A3.9 (Rse) Q4d. Table C4.11, Page C4-15, Medium Grade Steel Water at 75 0 C Note to Candidates: Please check the Programme Title and the Module Title to ensure that you have received the correct examination paper. If in doubt please contact an Invigilator. Page 1 of 10

2 Q1. (a) You have been given the responsibility of designing the water supply, storage and distribution for a previously unoccupied office building. One of the rooms on the ground floor of this two storey building is to be used as a staff canteen. Draw a neat sketch of a typical indirect cold water pipe work installation for such a building. Include the incoming line from the local authority mains, storage tank, sanitary fittings on both the ground floor and first floor, supply to canteen area, any recommended valves. [8 marks] (b) (c) (d) The hot and cold water distribution pipe work within this building could be designed as a gravity system or a pumped system. Different target water flow velocities can be applied to gravity or pumped systems. List one suggested target water flow velocity for each type of system. [2 marks] As part of the design of the water supply to this building you have been asked to carry out a HAZOP for the project. List five safety risks that could be identified during the design phase. For each risk describe the controls you would recommend to eliminate or minimise that safety risk. [5 marks] The sketch attached shows the cold water pipe work layout for an office building. Determine the most economical diameters of the copper distribution pipes labelled AB, BC, etc on the outlet of the storage tank. Assume an intermittent demand profile. Reference - Tables 1, 2, 3 and 4 Hot and Cold water pipe work design. Reference Table C4.18 Page C4-40 Flow of Water at 10 0 C in Copper Pipe. Fill in the relevant data on the Hot and Cold Water design spreadsheet supplied. Put your name on the sheet and attach the sheet to your answer book. [10 marks] Page 2 of 10

3 Q2 (a) (b) Draw a neat sketch of the typical construction detail for a cavity block work wall with partial fill insulation. Label all components. Label all resistance layers that should be considered when calculating the U-value of this construction from first principles. [8 marks] Technical Guidance Document L describes allowable U-values for various construction details. What is the current allowable U-value for :- i) External walls. (include units) ii) Ground floor. (include units) [2 marks] (c ) Technical Guidance Document L describes examples where thermal bridging occurs in domestic dwellings. i) Explain the term thermal bridging. [3 marks] ii) Draw a neat sketch to show a construction detail to prevent thermal bridging at a lintel over a window or door. [4 marks] (d) Calculate the U-value for the following construction. Please state the formula. 150mm thick flat concrete roof, k = 2.3 W/m 0 C. 15mm thick external layer of asphalt for waterproofing, k = 1.20 W/m 0 C. 10mm thick internal layer of plaster for decoration, k = 0.40 W/m 0 C. Heat flow vertically upwards. Reference - CIBSE Tables A3.8 (Rsi), A3.9 (Rse) [8 marks] Page 3 of 10

4 Q3 (a) Technical Guidance Document L, Diagram 1, shown U-values for the various heat loss surfaces of a dwelling. Draw a neat sketch to reproduce the heat loss surfaces shown in Diagram 1. Use arrows to indicate the direction of heat flow. It is not necessary to quote the U-values for these heat loss surfaces. [7 marks] (b) Technical Guidance Document L shows that the average U-value of 2.0 W/m 2 0 C for windows, doors and rooflights applies when the area of those elements equal to 25% of floor area. Average U-value of these elements may vary depending on their area relative to the floor area. Should the U-value be higher or lower if the area of these elements were equal to 35% of the floor area. Explain your answer. [ 4 marks] (c ) Failure to build modern dwellings in line with current building regulations will result in excessive use of energy and contribute to worldwide CO 2 emissions. List and explain three key issues addressed by current building regulations in order to minimise environmental impact. [6 marks] (d) Calculate the heat loss from the detached classroom shown in Fig 3.1 when the room is being heated using convection heating. [8 marks] 10m 8m INSIDE AIR TEMP 20 DEG C OUTSIDE DESIGN TEMP -1 C WINDOWS 2m x 1m. DOOR 2m x 1m. 3 AIR CHANGE PER HOUR. ROOM HEIGHT 3m. U VALUE WALLS WINDOWS DOOR FLOOR CEILING 2 W/M K FIG 3.1. HEAT LOSS DETACHED CLASSROOM QUESTION 3d Page 4 of 10

5 Q4 (a) (b) (c) (d) Draw a neat sketch of a fully pumped 2 pipe central heating system for a two storey dwelling. Include the heating circuit to an indirectly heated copper cylinder. Show cold water storage tank, indirect copper cylinder, fill and expansion tank, open vents, boiler, circulating pump and radiators on both floors. [7 marks] The circulating pump in a central heating system is used to move the required volumes of hot water and overcome all relevant pressure drops. Briefly explain how the overall pressure drop is calculated. [4 marks] As part of the design of a central heating system in a building you have been asked to consider the possible negative environmental impact which could occur. List three negative environmental issues that could occur. For each issue describe the controls you would recommend to eliminate or minimise that environmental issue. [6 marks] A two pipe insulated LPHW central heating system is shown in Fig 4.1. The pipe work is medium grade steel. The heat output from each radiator does not allow for a fixed percentage heat loss from the insulated pipe work supplying those radiators. Under the design conditions shown, find the following for pipe sections 1, 2 and 3. (i) Pipe diameter, (ii) Pressure drop per meter - dp l, (iii) Length equivalent factor - l e. Reference - Table C4.11, Page C4-15, Medium Grade Steel Water at 75 0 C. [8 marks] FIG 4.1 LPHW HEATING TWO PIPE PARALLEL SYSTEM OUTPUT 7 kw 6.0 m SECTION 1 (6m + 15m) x 2 SECTION 3 ( ) = 32.5m 15.0 m 8 m OUTPUT 12 kw SECTION 2 (8.0 m) x 2 1.0m 2.5m 12.5 m BOILER CIRCULATION PUMP ISOLATION VALVES TOTAL DISTANCE 4 METERS SPACE TEMPERATURE FLOW TEMPERATURE RETURN TEMPERATURE TARGET VELOCITY OF FLOW EMITTER HEAT CAPACITY SPECIFIC HEAT CAPACITY H DEG C 87 DEG C 70 DEG C 1 m/s AS SHOWN 4.2 kj/kg K Page 5 of 10

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CORK INSTITUTE OF TECHNOLOGY INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ. Summer Examinations 2009/10. Bachelor of Science in Process Plant Technology

CORK INSTITUTE OF TECHNOLOGY INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ Summer Examinations 2009/10 Module Title: Process Plant Services Module Code: MECH8018 School: Mechanical Engineering. Programme Title: Programme