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A Report on Masters of Engineering: Variable Refrigerant Flow System (VRF)

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Added on  2021-09-20

A Report on Masters of Engineering: Variable Refrigerant Flow System (VRF)

   Added on 2021-09-20

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A Report on
Masters of Engineering: Variable Refrigerant
Flow System (VRF)
Student Name:
Student ID:
Supervisor:
Submission Date:
A Report on Masters of Engineering: Variable Refrigerant Flow System (VRF)_1
Executive Summary
The spot light of this research is on simulating the VRF system energy consumption in energy-
plus software. The research ensures to review and examine the. Subsequently, it is required to
prove that, when in comparison with the other types of Air-con system which are currently in
use, the Variable Refrigerant Flow system is more energy efficient. However, this research’s
objective is to compare the energy consumption simulation data from energy-plus of VRF system
with the other two types of Air-con system. The splits system and centralized system are
considered. The advantages and the disadvantages of VRF systems in residential place are
investigated. The theoretical background, data analysis, design methodology are discussed. The
design details and results are also represented. The report concentrates that the conclusion has to
support the main focus of findings and possibility to use VRF in the residential building.
A Report on Masters of Engineering: Variable Refrigerant Flow System (VRF)_2
Acknowledgement
Table of Contents
A Report on Masters of Engineering: Variable Refrigerant Flow System (VRF)_3
1. Introduction..............................................................................................................................................................1
1.1 Problem Statement..............................................................................................................................................3
1.2 Research’s Aim and Scope...................................................................................................................................3
1.3 Research’s Objectives..........................................................................................................................................4
1.4 Theoretical Background......................................................................................................................................4
1.5 Dissertation Overview.........................................................................................................................................7
2. Literature Review.....................................................................................................................................................7
3. Design Methodology................................................................................................................................................13
3.1 Building Heat Load Analysis.............................................................................................................................14
3.2 Load Diversity..................................................................................................................................................14
3.3 Laboratory Testing............................................................................................................................................15
3.4 Example Laboratory Methodology....................................................................................................................16
3.5 Simulation and Validation Methodology............................................................................................................17
4. Model Development and Design Implementation.....................................................................................................18
4.1 Design Analysis.................................................................................................................................................18
4.2 Detail Design.....................................................................................................................................................22
4.2.1 The VRF-HP System Model......................................................................................................................22
4.2.2 The VRF-HR System Model.....................................................................................................................23
5. Concept Design.......................................................................................................................................................26
5.1 Variable Air Flow Heat Pump Computer Model................................................................................................26
5.2 Heating Operation............................................................................................................................................30
5.3 Implementation of Model in EnergyPlus............................................................................................................31
5.4 Model Development Workflow using Energy Plus.............................................................................................32
5.5 Prototyping and Model Validation.....................................................................................................................34
6. Comparison of VRF Systems...................................................................................................................................35
7. Advantages and Disadvantages of VRF System........................................................................................................38
7.1 Advantages of VRF System...............................................................................................................................38
7.2 Disadvantages of VRF System...........................................................................................................................41
8. Results and Discussion............................................................................................................................................42
9. Conclusions and Recommendations.........................................................................................................................46
A Report on Masters of Engineering: Variable Refrigerant Flow System (VRF)_4
References......................................................................................................................................................................48
List of Figures
Figure 1: VRF....................................................................................................................................................................3
Figure 2: Annual HVAC site energy savings for the VRF and RTU-VAV models; (A) HVAC total site energy, (B) heating site
energy, (C) cooling site energy, and (D) HVAC fan site energy savings potential of the VRF systems......................................14
Figure 4 Thermal Comfort Analysis...................................................................................................................................16
Figure 5 Thermal Comfort Analysis...................................................................................................................................16
Figure 6 Schematic chart of a 3-pipe VRF-HR system.........................................................................................................18
Figure 7 Variable Refrigerant Flow: An Emerging Air Conditioner and Heat Pump Technology..............................................21
Figure 8 Diagram of the direct expansion DX air handling unit (AHU)-water source variable refrigerant flow (VRF) system. SA:
supply air; RA: return air; EA: exhaust air; OA: outdoor air.................................................................................................24
Figure 9 Process of the modified Energy Plus.....................................................................................................................29
Figure 10 Cut-Away view of VRF outdoor unit with multiple Inverter Driven Compressors....................................................31
Figure 11 Compressor Operation at Part Load.....................................................................................................................32
Figure 12Comparing Rotary and Scroll Compressors..........................................................................................................32
Figure 13Compressor Efficiency: Rotary vs. Scroll.............................................................................................................33
List of Abbreviations
A Report on Masters of Engineering: Variable Refrigerant Flow System (VRF)_5
A Report on Masters of Engineering: Variable Refrigerant Flow System (VRF)_6
1. Introduction
Around the globe, for commercial construction projects, the VRF (Variable Refrigerant
Flow) systems turning into an inexorably mainstream HVAC solution. Because, this system is
offering numerous advantages which could be acknowledged by the engineers, architects, end
users and the contractors. Certain advantages for the end users are that, it contains flexible
installation, energy efficiency and local controls. However, there are common installation issues
which can be neglected when the other advantages are considered.
In general, the VRF systems are referred as multi-zone units which circulates the
refrigerant right from the outdoor compressor to various indoor fan coil units, depending on the
demand. Based on the application and building’s layout, various combination of indoor ductless
and ducted units could be utilized for such systems. The capacity of controlling the refrigerant
amount to be delivered to the unit of fan coil is present throughout the building, which makes
this VRF technology an ideal method for the applications that contains differing loads or where
zoning is required. For the applications which needs synchronous heating and cooling, the VRF
systems are accessible both, as the heat pump system or as the heat recovery system. For giving
prevalent convenience, the VRF systems delivers flexibility of design, energy consumption and
installation at cost effective price. This study ensures to highlight VRF system’s advantages, the
other advantages of the available advanced outdoor units and will suggest effective guidelines to
select the best option. The Variable Refrigerant Flow comprises of compressor and fan based
inverters which controls the system’s refrigerant flow as a response based on the demands of
cooling and heating. Hence, this allows to have effective performance of load over the
conventional and split-systems, when retaining highly precise temperature control (Danfoss.com,
2018).
The VRF with Heat Recovery innovation is a subset of VRF systems that enables the
individual indoor units to heat or cool as per the needs, whereas the compressor load profits due
to the inside heat recovery. A system of heat-recovery works by dealing with the refrigerant via,
the gas flow gadget, which could be heated and cooled simultaneously based on the necessities
of every single building zone. The heat recovery systems increments the efficiency of VRF by
means of energy exchange from one zone to address the issues of the other zone, while working
in synchronous heating and cooling mode. The VRF systems have modular design, where the
size of the compressor ranges from 6 to 30 tons and greater limit could be included as required
1
A Report on Masters of Engineering: Variable Refrigerant Flow System (VRF)_7
for the application by expanding the outdoor unit’s quantity. In contrast to the conventional
packaged multi-zone air conditioners systems have to condition all the zones and the supply air
should be reheated for oblige to varying temperature set points, the VRFs control every single
with the help of modulating the quantity of refrigerant which will be sent to every single fan loop
unit inside the zone. The delivery of refrigerant is regulated for deliver differing quantity of
refrigerant to the zones with a lower demand and different zones can be totally turned off when
there is partial to no cooling or heating demand. The inverter controlled compressor reacts to the
lower demand by decreasing its speed and results in a compelling decrease in capacity when
there is part-load conditions. In the non-proprietary building there is lack of energy simulation
tools and also lacks modelling capacity of VRF. Various efforts are put to build the VRF heat-
pump-system’s computer based model and consolidate it into the EnergyPlus engine’s unofficial
version. In DOE's EnergyPlusTM for the entire building energy simulation software, the VRF
heat-pump computer model was executed, and initially it was out during December 2011 as
V7.0.
The basics of VRF is that, it is categorized into the following components:
1) Outdoor units (condensing unit)
2) Indoor units (fan coils)
3) Refrigerant piping
4) Control
2
A Report on Masters of Engineering: Variable Refrigerant Flow System (VRF)_8

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