MECH4880 REFRIGERATION AND AIR CONDITIONING

ASSIGNMENT 1 (2024) – Assignment Helper (Ver 2)

Aim

The purpose of this document is to provide a more detailed explanation of the minimum project requirements in a partially stepped-out manner.

This document outlines two main types of questions to follow:

• Discuss questions  are  designed  to  give  you  some  direction  for  what  to  do  next  while developing  your  understanding  of  the  concept.  Discuss  questions  should  typically  be answered in a maximum of one paragraph, while the depth of your understanding and research should be demonstrated in your response, keeping your answer succinct is also a critical part of explaining and reporting engineering findings.

• Perform questions, which usually follow from discuss questions, are designed to use the understanding you develop from the discuss question and complete that section of the report.

Preceding the breakdown of both parts of the assignment is a list of assumptions already made for your assignment; take care in reading and understanding them, as they can greatly simplify the work you need to complete.

Part A – Hand Calculations and Simulation

Section 1 – Fundamentals and Manual Analysis

(1) – Design Day Selection and Specification Comprehension

Discuss: What are design days, and what is their significance to heat load calculation? Perform.: Select the summer and winter design days for the project.

Discuss: What are the design conditions (Internal and external) for the project?

Discuss: Calculate the size of the building’s ceiling space and explain its purpose.

Discuss: Define and explain the following terms: storage mass, AHU and damper.

Perform.: Specify the daily and yearly temperature ranges you are going to use for the analysis and briefly describe why you are using those values.

(2) – External Loads – Wall Specifications

Discuss: What is the difference between a U-value and an R-value?

Discuss: How are R-values calculated for walls that have differing materials in parallel? Discuss: How does outdoor wind speed affect U-values for a given material?

Perform. Calculate and report the U-values for all surfaces in the Gym.

Perform: Using NCC 2022 Volume One, determine the minimum R-values for a typical wall, roof and floor (Hint: Sections J4D4, J4D6 and J4D7). Specify the wall, roof and floor type and their applicational scenarios.

Discuss: Why does the NCC provide minimum R-values?

Perform.: For any surface that does not meet the minimum requirements, add increments of R=0.5 insulation until the surface meets the minimum specification. Provide a list of the updated U-values for all surfaces.

Perform. Calculate and report the storage masses for all surfaces in the Gym.

(3) – External Loads – Conduction and Solar Transmission Discuss: Which surfaces will experience solar transmission loads?

Discuss: Surfaces external to the structure use a modified temperature difference when calculating their contribution to the heat loads. What does this modified temperature difference account for, and how does it affect heat load (increased/decreased)?

Discuss: How is the heat load for external glazing calculated? State the full formula and explain each component.

Perform. Calculate and report the heat load for all external surfaces in the Gym.

(4) – External Loads – Partitions

Discuss: What  is  the  difference  between  partitions  and  external  surfaces?  How  do  heat  load calculations differ between partitions and external surfaces?

Perform. Calculate and report the heat load for all partitions in the Gym.

(5) – External Loads – Winter

Discuss: Discuss three key differences between calculating external loads for cooling (summer) and heating (winter).

Perform. Calculate and report the external loads under winter conditions for the Gym.

(6) – Internal Loads – Summer

Discuss: Not including infiltration, what are the three main forms of internal loads, and how would the heat load be calculated from the provided information?

Perform. Calculate and report all internal loads and infiltration loads in the Gym.

(7) – Internal Loads – Winter

Discuss: Discuss three key differences between calculating internal loads for cooling (summer) and heating (winter).

Perform. Calculate and report all internal and infiltration loads under winter conditions in the Gym.

(8) – Cooling and Heating Load Summary

Perform. Report a summarised version of your findings and determine the total heating and cooling load required for the Gym.

(9) – Psychrometric Charts (Summer only)

Discuss: Discuss the features of psychrometric charts and the information they can provide.

Perform.: Produce  psychrometric   charts  for  the  peak   summer  loading  cases,  reporting  any intermediate values and clearly indicating all points on the chart and their values.

Perform. Calculate the reheat capacity (if required) and the total cooling coil load.

(10) – CAMEL heat load validation for Planet Gym (Gym)

Discuss: This project uses the comfort temperature conditions defined by CAMEL. What are the critical conditions, how are they measured, and under what circumstances would you use them?

Discuss: Discuss any possible reasons for variations in comparing your calculations with the CAMEL simulation results provided. Are your results the same? If they are not, why? (Hint: there are different result types produced by CAMEL).

Discuss: The specification states that safety factors and diversity will not be used. Define each term and discuss the impacts on the duct, AHU, and system cost for introducing each.

Part B – System Design and Sustainability

Section 1 – Zoning and Simulation Analysis

(1) - Produce conditioned/ventilated space maps and discuss on thermal zone plans

Discuss: Define and compare conditioned and ventilated spaces; give two examples of spaces/room types for each.

Perform.: Using two different colours, preferably blue for conditioned and red for ventilated, produce an overlay of the building floor plans showing all conditioned and ventilated spaces. Are there any spaces on the building plan which are neither conditioned nor ventilated?

Discuss: What is thermal zoning, and what information does it provide when setting up heat load calculations?

(2) Design Brief for the whole building

Discuss: Briefly discuss the following features of the building: where are the partitions (those that will add to the heat load), which rooms will have roof loads, how many skylights are there, and which spaces do they interact with. Also briefly discuss how the functionality of the room (i.e., use of room, occupation group, equipment etc.) affect the room heat load.

Perform. Using the conclusion from the discussion, prepare a design brief for the whole shopping centre,  identify  the  key  considerations/factors  that  contributes  to  heat  load  estimation  when designing the HVAC system and, propose and justify one possible thermal zone in the building (not including the gym)

Perform.: Propose  in  your  design  brief 2-4  suggestions  to reduce  the  required  cooling capacity of the building without compromising the building performance.

(3) - Ventilated space calculations

Discuss: Consulting table 3.2 in AS 1668.2 – 2012, what is the smallest number of exhaust systems that can be installed to serve all ventilated spaces.

Discuss: Does the lift shaft require mechanical ventilation? What are some of the factors that may lead to heat gain within a lift shaft? Hint: You may consult NCC 2022 Specification E3D2.

Perform: Using the appropriate appendices from AS 1668.2 – 2012, calculate and report the exhaust rate (L/s) for each ventilated space within the building.

Section 2 – Schematics and Duct Design

(4) - Air schematics

Discuss: What is the purpose of an air schematic? What information can it provide?

Produce: Construct a separate or combined full air schematics for the supply and ventilation of the building. All equipment serving these rooms must be represented on the schematic, complete with all the spaces they serve. The schematic should show, at a minimum, the airflow into the Gym and the flow rates for all relevant exhaust fans (Ventilated Space ONLY).

(5) - Duct Design

Discuss: Why are different maximum airspeeds used for main ducts and branch ducts?

Discuss: What are the pros/cons of reducing duct size for the same airflow? What are the pros/cons of increasing duct size for the same airflow?

Perform.: Construct a single-line duct layout and preliminary duct sizes for supply, outside air and exhaust systems, indicating duct size and flow rate for the Gym. Perform the same for the exhaust ducts for the building's ventilated spaces.

Section 3 – Duct Analysis, System Selection and Sustainability

(6) - Pressure loss calculations and fan selection (Ventilated spaces only)

Discuss: In terms of duct pressure loss calculations, what is an index run (equal friction method)?

Discuss: Why is the index run pressure drop used  as the pressure drop  for the  entire  system? How can we achieve this pressure drop at each outlet to ensure the correct airflow (equal friction method)?

Perform. Indicate the index run on the previously drawn supply system and all exhaust duct systems.

Discuss: Pressure losses are due to two main causes, straight duct and duct fittings, provide the formula for both and explain each term.

Perform.: For ventilated spaces only, calculate and report the pressure loss (equal friction method) along the index run. Only the losses for the rigid duct should be counted,i.e. ignore any pressure losses associated with intakes, grilles, flexible connections, etc. Add  100 Pa pressure drop onto your final value to compensate for this assumption.

Discuss: Briefly discuss three important factors/considerations in duct design and how these could be/have been implemented in the duct layout produced for the previous section.

Perform.: Select and report fan requirements for each pressure loss calculation and justify their selection based on the previous discussion question. (Hint: you only need to provide at least pressure drop and flow rate.)

Discuss: Discuss three important factors when selecting a fan.

(7) - AHU selection

Discuss: What are the three of the most important parameters (do not discuss cost) to consider when selecting an AHU?

Produce: Select appropriate AHUs for the Gym. The unit selected should, as a minimum, meet the capacity and airflow required. The unit can be assumed to be air-cooled or connected to a chiller system based on your AHU selection (Note: you do not need to design or select any associated equipment).

Discuss: What is the economy cycle? What is different about AHUs or the surrounding system with economy cycles?

(8) - Building improvements and sustainable design

Discuss: What building features have the most significant heat load, and what improvements could you make to mitigate their impact? (1 paragraph per feature, minimum 3 features)

Discuss: Would reducing the air off temperature (reducing the coil temperature) reduce the cooling capacity required? Why/why not?

Discuss: Based on the preliminary CFD analysis provided, discuss your understanding of the current design, with focus on the flow behaviour and thermal comfort. What improvements can be made in actual design and installation by implementing the insight from CFD results? Identify possible design flaws in the current system and their impact.

Discuss: Briefly describe two rating schemes that have been implemented in the building industry in order to encourage sustainability. Discuss their impact on HVAC system design and to what extent you think they have been successful. (2 paragraphs maximum)

Assumptions:

1.   All kitchen exhausts are considered out of scope

2.   FCU’s and AHU’s can be assumed to have the same function and features and so only AHU’s need to be used

3.   All  duct  is  designed  to  be  rectangular/square  and  in  increments  of  no  less  than  50mm  (e.g. 325x350mm is not allowed, but 450x600mm is), and flexible duct is not required to be sized.

4.   Duct design does not require economy cycle.

5.   “DA09 infiltration”: infiltration through walls and windows only needs to be applied for the gym considered in the hand calculations.

6.   For Part A only, all glass (internal and external) can be treated as 6mm plate type, as defined by DA09.

7.   For the purpose of hand calculations, please assume the false ceiling space to be void (you should still justify why this is appropriate).

8.   Several spaces require pressure differentials, and these are all out of scope. Simply achieve the required airflow as per the heat loads that you calculate. Air change requirements, however, should be met.

9.   For internal loads, all equipment listed should be referenced from the quoted ASHRAE document first, followed by DA09 and any external source.

10. Grille selection is outside of scope.

11. All AHUs are to be served by chilled water systems, and all water systems within the building are out of scope.

12. Façade shading: the structures are solar fins and are similar in nature to those shown below in the two images [1] [2].

13. On making your own assumptions: As a general rule of thumb, if it is not in the assignment documents, just make the assumption that will make your calculations the easiest possible while  still being  justifiable. Extending from this, the assignment helper can be used as a tool to identify the key elements  that we are looking for; while you will have to perform. some tasks out of the listing, try to maximise  your use of time by not overdoing or over-detailing these sections.

References:

[1] “ Exterior        Shutters        We         Love!”, Pinterest,         2016.        [Online].         Available:

https://au.pinterest.com/pin/363313894911151079/. [Accessed: 17- Oct- 2016].

[2] “Aluminum solar shading / facade - Alumet Renewable  Energy Technologies” ,Archiexpo.com, 2016.         [Online].          Available: http://www.archiexpo.com/prod/alumet-renewable-energy- technologies/product- 69637-537603.html. [Accessed: 17- Oct- 2016].