# Internal Heat Exchanger Influence in Operational Cost and Environmental Impact of an Experimental Installation Using Low GWP Refrigerant for HVAC Conditions

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## Abstract

**:**

## 1. Introduction

## 2. Characteristics of R1234ze(E) as an Alternative Refrigerant

^{®}software (NIST—Gaithersburg, MA, USA) [17].

#### Environmental Effects

_{2}emissions from the use of electrical energy for the operation of the system. Lastly, the LCCP considers, in addition to direct emissions, the emissions caused indirectly by using each fluid and the refrigeration system, while also considering all the relevant indirect emissions involved in the life cycle of the refrigerant compared to the TEWI, such as emissions related to the manufacture and disposal of this, as well as the life use of the system. This is how, in this paper, the LCCP analysis of the environmental impact generated by operating refrigerants R134a and R1234ze(E) under the proposed operating conditions is carried out. Here we seek to observe the influence represented by the low GWP of R1234ze(E) and the refrigerant charge of the system for each configuration, as well as the impact on indirect emissions due to energy consumption and the inclusion of the IHX for each refrigerant based on its thermal performance for each cycle.

## 3. Experimental Procedure

^{3}/h of displacement volume, two plate heat exchangers that act as condenser and evaporator of 3.5 kW and 2.5 kW capacity, respectively, a 3-L capacity liquid receiver, and a 5.0 kW nominal capacity thermostatic expansion valve. Finally, an internal heat exchanger was added, which is a plate and has a capacity of 2.5 kW. All plate heat exchangers are arranged to operate in countercurrent. Table 3 shows the main characteristics of the heat exchangers that are part of the experimental installation.

- -
- BRC.
- -
- IHXC.

#### 3.1. Basic Refrigeration Cycle (BRC)

#### 3.2. Use of an IHX as Improvement on BRC

## 4. Integral Analysis

#### 4.1. Energy Study

#### 4.2. Exergy Study

_{o}, P

_{o}). In this case, chemical, magnetic, electrical, and nuclear exergy are neglected. The physical exergy of a flow stream can be expressed as:

#### 4.3. Exergoeconomic Study

#### 4.4. Life Cycle Climate Performance Study

_{2eq}or the SLCCP in kgCO

_{2eq}/kWh.

_{2eq}/kg), and adp.GWP is the GWP of the atmospheric degradation product of the refrigerant (kgCO

_{2eq}/kg).

_{2eq}/kWh). EM is calculated from the share of resources for power plants in the electricity generation region.

_{2eq}produced/kg of material (kgCO

_{2eq}/kg), m is the mass of the unit/material (kg), RM is the CO

_{2eq}produced/kg of recycled material (kgCO

_{2eq}/kg), Mr is the mass of recycled material (kg), RFM represents the emissions from the manufacture of the refrigerant (kgCO

_{2eq}/kg), and RFD represents the emissions from the disposal of the refrigerant (kgCO

_{2eq}/kg).

## 5. Results

#### 5.1. Cooling Capacity

_{min;mix}= 0.141 L/s and C

_{max;mix}= 0.162 L/s). In this case, when operating the IHXC, it was found that due to the sub-cooling at the condenser outlet caused by the IHX, the enthalpy at the evaporator inlet is reduced, and the smaller this value, the higher the increase in the cooling capacity. Likewise, when the evaporation temperature increases, the cooling capacity also increases. It is also highlighted that for the R1234ze(E) to match the cooling capacity obtained by the R134a in the BRC, it is necessary to implement the IHXC to match this performance parameter.

_{max;mix}= 0.162 L/s), an increase is observed in the cooling capacity for the cycles operated in a range of 3.1% to 5.6% regarding the results obtained with the minimum flow condition of the mixture, which suggests that the increase in volumetric flow improves the energy transfer in the evaporator. Similarly, for this flow condition, the inclusion of the IHX is necessary so that the cooling capacity of R1234ze(E) reaches that of R134a operating in the BRC. Considering properties that influence the improvement of the cooling capacity is the thermal conductivity of liquid and vapor, and R1234ze(E) has a lower thermal conductivity of liquid compared to R134a, presenting lower values in this performance parameter; however, in the case of vapor thermal conductivity, it is slightly higher for R1234ze(E), and with the help of IHX, it is possible to match the cooling capacity.

#### 5.2. Coefficient of Performance (COP)

_{max;mix}= 0.162 L/s), the flow condition for which a higher cycle performance is obtained without requiring a large difference in flow power in the thermal load simulator circuit concerning that used for the minimum flow condition. The favorable effect of the subcooling caused by activating the IHX within the cycle can be appreciated, producing an increase in the cooling capacity in the evaporator. In the same way, increasing the evaporation temperature produces a lower requirement in the compression work, thus contributing to the increase in the COP. When comparing R1234ze(E) and R134a operating the BRC, there is a reduction in the COP between 3.3% and 5.5%, and when including the IHX using R1234ze(E), these differences are reduced by between 0.32% and 1.5%. Similarly, by incorporating the IHX and presenting a lower liquid density with respect to R134a, a reduction in the refrigerant charge required for the two cycle configurations is observed, with which a lower flow power is needed, thus improving the COP.

#### 5.3. Exergy Efficiency

#### 5.4. Destruction of Exergy

#### 5.5. Operational Costs

#### 5.6. LCCP Evaluation

_{2eq}for each of the refrigerants is analyzed using specific LCCP (SLCCP), which was calculated by dividing total emissions by the amount of kWh consumed by the unit. Due to the high GWP of R134a, it is noted that it influences the impact of direct emissions when operating with this refrigerant. The improvement in total direct emissions when using R1234ze(E) compared to R134a is close to 100%. Another very useful aspect that Table 9 provides is the great influence of the energy consumption factor. Even though operation with R1234ze(E) implied a minimum reduction in energy consumption of approximately 3%, reducing this factor for the operation of the system implies an opportunity for improvement of the cycle, focused both on the thermal performance and the substantial reduction in the negative impact on the environment. This could be addressed by using a new configuration or modification of the compression cycle, in such a way that the energy consumption of the system can be reduced. Considering the total emissions of kgCO

_{2eq}per kWh required to operate the system, a reduction in this specific climate performance parameter is presented when using R1234ze(E) relative to R134a. When the BRC is operated, the reduction is between 0.7% and 8.2%, and for the IHXC configuration, the reduction varies between 8.8% and 18.5% for the evaporation conditions considered.

## 6. Conclusions

_{2eq}for the two refrigerants. The highlighted conclusions are summarized below.

_{2eq}by 10.7% compared to R134a. Direct emissions and energy consumption are the major contributors to the LCCP, establishing an opportunity for improvement for future research. The SLCCP of R1234ze(E) in IHXC mode compared to BRC and R134a showed a reduction of between 9.1% and 13.3% for the evaporation range considered.

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## Nomenclature

A | amps |

$\mathrm{C}$ | flow, L/s |

$\mathrm{c}$ | unit exergy cost, $/kJ |

$\stackrel{.}{\mathrm{C}}$ | exergy cost rate, $/h |

$\mathrm{Ch}$ | refrigerant charge, kg |

$\mathrm{DE}$ | direct emissions, kgCO_{2eq} |

$\stackrel{.}{\mathrm{E}}$ | exergy rate, kW |

$\mathrm{EM}$ | power plant emission factor, kgCO_{2eq}/kWh |

$\mathrm{h}$ | specific enthalpy, kJ/kg |

$\mathrm{IE}$ | indirect emissions, kgCO_{2eq} |

${\mathrm{i}}_{\mathrm{r}}$ | interest rate, % |

$\mathrm{L}$ | average lifetime of equipment, year |

$\stackrel{.}{\mathrm{m}}$ | mass flow rate, kg/s |

$\mathrm{M}$ | mass of unit or material, kg |

$\mathrm{MM}$ | CO_{2e} produced per kg of material, kgCO_{2eq}/kg |

$\mathrm{Mr}$ | mass of recycled material, kg |

$\mathrm{n}$ | lifetime, year |

$\mathrm{P}$ | pressure, kPa |

$\stackrel{.}{\mathrm{Q}}$ | heat transfer, kW |

$\mathrm{s}$ | specific entropy, kJ/kg-K |

${\mathrm{t}}_{\mathrm{ope}}$ | annual operating time, h |

$\mathrm{T}$ | temperature, °C |

V | volts |

$\stackrel{.}{\mathrm{W}}$ | power consumption, kW |

$\mathrm{Z}$ | purchase cost associated with a component, $ |

$\stackrel{.}{\mathrm{Z}}$ | capital cost rate, $/h |

Abbreviations | |

$\mathrm{Adp}.\mathrm{GWP}$ | GWP of atmospheric degradation product of the refrigerant: kgCO_{2eq}/kg |

$\mathrm{AEC}$ | annual energy consumption, kWh |

$\mathrm{ALR}$ | annual leakage rate, % of refrigerant charge |

BRC | basic refrigeration cycle |

COP | coefficient of performance |

CRF | capital recovery factor |

$\mathrm{EOL}$ | end of life refrigerant leakage, % of refrigerant charge |

GWP | global warming potential |

HFC | hydrofluorocarbon |

HFO | hydrofluoroolefin |

IHXC | cycle with internal heat exchanger |

IIR | institute of international refrigeration |

LCCP | life cycle climate performance |

ODP | ozone depletion potential |

$\mathrm{RFD}$ | refrigerant disposal emissions per unit mass of refrigerant, kgCO_{2eq}/kg |

$\mathrm{RFM}$ | refrigerant manufacturing emissions per unit mass of refrigerant, kgCO_{2eq}/kg |

$\mathrm{SLCCP}$ | specific life cycle climate performance, kgCO_{2eq}/kWh |

SUB | subcooling |

SUP | superheating |

$\mathrm{TCR}$ | total cost rate, $/h |

TEV | thermostatic expansion valve |

Subscripts | |

CI | capital investment |

cold | cold stream |

comp | compressor |

cond | condenser |

D | destruction |

eq | equivalent |

evap | evaporator |

f | fuel |

hot | hot stream |

in | inlet |

iso | isentropic |

$\mathrm{k}$ | component |

max | maximum |

min | minimum |

mix | mixture |

o | ambient |

OM | operation and maintenance |

out | outlet |

p | product |

PH | physical |

ref | refrigerant |

TOT | total |

$\mathrm{wat}$ | water |

wgm | water-glycol mixture |

Greek symbols | |

$\mathsf{\epsilon}$ | effectiveness |

$\mathsf{\u03f5}$ | efficiency |

$\mathsf{\phi}$ | operation and maintenance cost factor |

$\mathsf{\psi}$ | rational efficiency |

## References

- European Commission. Regulation (EU) No 517/2014 of the European Parliament and the Council of 16 April 2014 on fluorinated greenhouse gases and repealing Regulation (EC) No 842/2006. Off. J. Eur. Union
**2014**, L150, 195. [Google Scholar] - UNEP (United Nations Environment Programme). Twenty-Eighth Meeting of the Parties to the Montreal Protocol on Substances that Deplete the Ozone Layer. Furth. Amend. Montr. Protoc.
**2016**, 1–72. Available online: https://ozone.unep.org/sites/default/files/2019-08/MOP-28-12E.pdf (accessed on 20 March 2022). - Liu, W.; Meinel, D.; Wieland, C.; Spliethoff, H. Investigation of hydrofluoroolefins as potential working fluids in organic Rankine cycle for geothermal power generation. Energy
**2014**, 67, 106–116. [Google Scholar] [CrossRef] - Mota-Babiloni, A.; Navarro-Esbrí, J.; Molés, F.; Cervera, Á.B.; Peris, B.; Verdú, G. A review of refrigerant R1234ze(E) recent investigations. Appl. Therm. Eng.
**2016**, 95, 211–222. [Google Scholar] [CrossRef] - Mota-Babiloni, A.; Navarro-Esbrí, J.; Barragán, Á.; Molés, F.; Peris, B. Drop-in energy performance evaluation of R1234yf and R1234ze(E) in a vapor compression system as R134a replacements. Appl. Therm. Eng.
**2014**, 71, 259–265. [Google Scholar] [CrossRef] [Green Version] - Sánchez, D.; Cabello, R.; Llopis, R.; Arauzo, I.; Catalán-Gil, J.; Torrella, E. Energy performance evaluation of R1234yf, R1234ze(E), R600a, R290 and R152a as low-GWP R134a alternatives. Int. J. Refrig.
**2017**, 74, 269–282. [Google Scholar] [CrossRef] - Devecioglu, A.G.; Oruc, V. Improvement on the energy performance of a refrigeration system adapting a platetype heat exchanger and low-GWP refrigerants as alternatives to R134a. Energy
**2018**, 155, 105–116. [Google Scholar] [CrossRef] - Colombo, L.P.M.; Lucchini, A.; Molinaroli, L. Experimental analysis of the use of R1234yf and R1234ze(E) as drop-in alternatives of R134a in a water-to-water heat pump. Int. J. Refrig.
**2020**, 115, 18–27. [Google Scholar] [CrossRef] [Green Version] - Sethi, A.; Vera Becerra, E.; Yana Motta, S. Low GWP R134a replacements for small refrigeration (plug-in) applications. Int. J. Refrig.
**2016**, 66, 64–72. [Google Scholar] [CrossRef] - Nawaz, K.; Shen, B.; Elatar, A.; Baxter, V.; Abdelaziz, O. R-1234yf and R-1234ze(E) as low-GWP refrigerants for residential heat pump water heaters. Int. J. Refrig.
**2017**, 82, 348–365. [Google Scholar] [CrossRef] - Jribi, S.; Saha, B.B.; Koyama, S.; Chakraborty, A.; Ng, K.C. Study on activated carbon/HFO-1234ze(E) based adsorption cooling cycle. Appl. Therm. Eng.
**2013**, 50, 1570–1575. [Google Scholar] [CrossRef] - Fukuda, S.; Kondou, C.; Takata, N.; Koyama, S. Low GWP refrigerants R1234ze(E) and R1234ze(Z) for high temperature heat pumps. Int. J. Refrig.
**2013**, 40, 161–173. [Google Scholar] [CrossRef] - Le, V.L.; Feidt, M.; Kheiri, A.; Pelloux-Prayer, S. Performance optimization of low-temperature power generation by supercritical ORCs (organic Rankine cycles) using low GWP (global warming potential) working fluids. Energy
**2014**, 67, 513–526. [Google Scholar] [CrossRef] - Abdalla, G. Performance Characteristics of Automotive Air Conditioning System with Refrigerant R134a and Its Alternatives. Int. J. Energy Power Eng.
**2015**, 4, 168–177. [Google Scholar] - Kasaeian, A.B.; Daviran, S. Performance Analysis of Solar Combined Ejector-Vapor Compression Cycle Using Environmental Friendly Refrigerants. IIUM Eng. J.
**2013**, 14, 93–103. [Google Scholar] [CrossRef] - Direk, M.; Soylu, E. The effect of internal heat exchanger using R1234ze(E) as an alternative refrigerant in a mobile air-conditioning system. J. Mech. Eng.
**2018**, 64, 114–120. [Google Scholar] - Lemmon, E.W.; Bell, I.H.; Huber, M.L.; McLinden, M.O. NIST Standard Reference Database 23: Reference Fluid Thermodynamic and Transport Properties-REFPROP; Version 10.0; National Institute of Standards and Technolog: Gaithersburg, MA, USA, 2018.
- Bolaji, B.O. Theoretical assessment of new low global warming potential refrigerant mixtures as eco-friendly alternatives in domestic refrigeration systems. Sci. Afr.
**2020**, 10, e00632. [Google Scholar] [CrossRef] - Zyczkowski, P.; Borowski, M.; Luczak, R.; Kuczera, Z.; Ptaszynski, B. Functional Equations for Calculating the Properties of Low-GWP R1234ze(E) Refrigerant. Energies
**2020**, 13, 3052. [Google Scholar] [CrossRef] - Bobbo, S.; Di Nicola, G.; Zilio, C.; Brown, J.S.; Fedele, L. Low GWP halocarbon refrigerants: A review of thermophysical properties. Int. J. Refrig.
**2018**, 90, 181–201. [Google Scholar] [CrossRef] - Liu, Y.; Wen, J.; Xu, P.; Khan, M.; Wang, S.; Tu, J. Numerical investigation on the condensation of R134a, R1234ze(E) and R450A in mini-channels. Int. J. Refrig.
**2021**, 130, 305–316. [Google Scholar] [CrossRef] - Tsatsaronis, G. Definitions and nomenclature in exergy analysis and exergoeconomics. Energy
**2007**, 32, 249–253. [Google Scholar] [CrossRef] - Bejan, A.; Tsatsaronis, G.; Moran, M.J. Thermal Design and Optimization; John Wiley and Sons: New York, NY, USA, 1996. [Google Scholar]
- Kotas, T.J. The Exergy Method of Thermal Power Plants Analysis; Krieger Publ. Co.: Malabar, FL, USA, 1995. [Google Scholar]
- Fazelpour, F.; Morosuk, T. Exergoeconomic analysis of carbon dioxide transcritical refrigeration machines. Int. J. Refrig.
**2014**, 38, 128–139. [Google Scholar] [CrossRef] - Ahmadzadeh, A.; Reza Salimpour, M.; Sedaghat, A. Thermal and exergoeconomic analysis of a novel solar driven combined power and ejector refrigeration (CPER) system. Int. J. Refrig.
**2017**, 83, 143–156. [Google Scholar] [CrossRef] - Mousavi, S.A.; Mehrpooya, M. A comprehensive exergy based evaluation on cascade absorption compression refrigeration system for low temperature applications—Exergy, exergoeconomic, and exergoenvironmental assessments. J. Clean. Prod.
**2020**, 246, 119005. [Google Scholar] [CrossRef] - Makhnatch, P.; Khodabandeh, R. The role of environmental metrics (GWP, TEWI, LCCP) in the selection of low GWP refrigerant. Energy Procedia
**2014**, 61, 2460–2463. [Google Scholar] [CrossRef] [Green Version] - IIR (International Institute of Refrigeration). Guideline for Life Cycle Climate Performance; International Institute of Refrigeration: Paris, France, 2016. [Google Scholar]
- Troch, S.; Lee, H.; Hwang, Y.; Radermacher, R. Harmonization of Life Cycle Climate Performance (LCCP) Methodology. Int. J. Refrig. Air Cond. Conf.
**2016**, 1724. Available online: http://docs.lib.purdue.edu/iracc/1724 (accessed on 20 March 2022). - Lee, H.; Troch, S.; Hwang, Y.; Radermacher, R. LCCP evaluation on various vapor compression cycle options and low GWP refrigerants. Int. J. Refrig.
**2016**, 70, 128–137. [Google Scholar] [CrossRef] - Choi, S.; Oh, J.; Hwang, Y.; Lee, H. Life cycle climate performance evaluation (LCCP) on cooling and heating systems in South Korea. Appl. Therm. Eng.
**2017**, 120, 88–98. [Google Scholar] [CrossRef]

**Figure 1.**Experimental installation: (

**a**) Refrigeration circuit, (

**b**) thermal load simulator, and (

**c**) thermal load sink.

**Figure 3.**(

**a**) P-h diagram of basic refrigeration cycle, (

**b**) scheme of basic refrigeration cycle (BRC) in experimental installation.

**Figure 5.**Variation of the cooling capacity for the two flow conditions of the water–glycol mixture.

**Figure 6.**Destruction of exergy in each component of the BRC and IHXC using (

**a**) R134a, (

**b**) R1234ze(E).

Property | R134a (HFC) | R1234ze(E) (HFO) |
---|---|---|

ASHRAE Safety Group | A1 | A2L |

GWP | 1300 | <1 |

ODP | 0 | 0 |

Critical pressure (kPa) | 4059.3 | 3634.9 |

Critical temperature (K) | 374.2 | 382.5 |

Boiling point at 1 atm (K) | 247.1 | 253.9 |

ASHRAE Flammability | No | Low |

ASHRAE Toxicity | No | No |

Molecular weight (kg/kmol) | 102 | 114 |

Liquid density * (kg/m^{3}) | 1294.8 | 1240.1 |

Vapor density * (kg/m^{3}) | 14.4 | 11.7 |

Specific heat of liquid * (kJ/kgK) | 1.34 | 1.34 |

Specific heat of vapor * (kJ/kgK) | 0.897 | 0.897 |

Latent heat of vaporization (kJ/kg) | 198.6 | 184.2 |

Liquid thermal conductivity * (kJ/kgK) | 92 × 10^{−3} | 83.1 × 10^{−3} |

Vapor thermal conductivity * (kJ/kgK) | 11.5 × 10^{−3} | 11.6 × 10^{−3} |

Liquid viscosity * (Pa/s) | 266.5 × 10^{−6} | 262.6 × 10^{−6} |

Vapor viscosity * (Pa/s) | 10.7 × 10^{−6} | 10.7 × 10^{−6} |

**Table 2.**Specifications of the elements and devices for measuring temperature, pressure, flow, and electrical power.

Sensor | Specification | Measuring Range | Sensitivity |
---|---|---|---|

Temperature | Thermocouple type K | −270 to 1372 °C | 3.6 mV/100 °C |

Pressure | WIKA | 0 to 25 bar and 0 to 100 bar | ≤±0.3% |

Coriolis flowmeter | SITRANS FC Coriolis | 4500 kg/h | ±0.2% with liquids and ± 0.4% with gases |

Electromagnetic flowmeter (Secondary circuits) | ONICON | 0.1 to 0.6 kg/s | ±0.4% |

Power measurement | FLUKE 1736 | 1000 V and 40 A | ±0.2% V and ±0.7% A |

Component | Specification | Number of Plates | Dimensions (cm) (Length × Width × Height) |
---|---|---|---|

Evaporator | PHE B3-030-10 | 10 | 32.5 × 9.5 × 2.4 |

Condenser | PHE B3-030-20 | 20 | 32.5 × 9.5 × 3.9 |

IHX | PHE B3-030-10 | 10 | 32.5 × 9.5 × 2.4 |

Component | Model | Energy Analysis | Exergy Analysis | Exergoeconomic Analysis |
---|---|---|---|---|

Compressor | ${\mathrm{n}}_{\mathrm{iso}}=\frac{{\mathrm{h}}_{\mathrm{out};\mathrm{iso}}{-\mathrm{h}}_{\mathrm{in}}}{{\mathrm{h}}_{\mathrm{out}}{-\mathrm{h}}_{\mathrm{in}}}$ ${\stackrel{.}{\mathrm{W}}}_{\mathrm{c}\mathrm{o}\mathrm{m}\mathrm{p}}={\stackrel{.}{\mathrm{m}}}_{\mathrm{r}\mathrm{e}\mathrm{f}}{({\mathrm{h}}_{\mathrm{o}\mathrm{u}\mathrm{t}}-{\mathrm{h}}_{\mathrm{i}\mathrm{n}})}_{\mathrm{c}\mathrm{o}\mathrm{m}\mathrm{p}}$ | ${\stackrel{.}{\mathrm{W}}}_{\mathrm{c}\mathrm{o}\mathrm{m}\mathrm{p}}-({\stackrel{.}{\mathrm{E}}}_{\mathrm{o}\mathrm{u}\mathrm{t}}-{\stackrel{.}{\mathrm{E}}}_{\mathrm{i}\mathrm{n}})={\stackrel{.}{\mathrm{E}}}_{\mathrm{D};\mathrm{c}\mathrm{o}\mathrm{m}\mathrm{p}}$ | ${\stackrel{.}{\mathrm{C}}}_{\mathrm{o}\mathrm{u}\mathrm{t}}={\stackrel{.}{\mathrm{C}}}_{\mathrm{i}\mathrm{n}}+{\stackrel{.}{\mathrm{C}}}_{\mathrm{w};\mathrm{c}\mathrm{o}\mathrm{m}\mathrm{p}}+{\stackrel{.}{\mathrm{Z}}}_{\mathrm{c}\mathrm{o}\mathrm{m}\mathrm{p}}$ | |

Condenser | ${\stackrel{.}{\mathrm{Q}}}_{\mathrm{c}\mathrm{o}\mathrm{n}\mathrm{d}}={\stackrel{.}{\mathrm{m}}}_{\mathrm{r}\mathrm{e}\mathrm{f}}{({\mathrm{h}}_{\mathrm{i}\mathrm{n}}-{\mathrm{h}}_{\mathrm{o}\mathrm{u}\mathrm{t}})}_{\mathrm{c}\mathrm{o}\mathrm{n}\mathrm{d}}$ | $({\stackrel{.}{\mathrm{E}}}_{\mathrm{i}\mathrm{n}}-{\stackrel{.}{\mathrm{E}}}_{\mathrm{o}\mathrm{u}\mathrm{t}})-({\stackrel{.}{\mathrm{E}}}_{\mathrm{w}\mathrm{a}\mathrm{t};\mathrm{o}\mathrm{u}\mathrm{t}}-{\stackrel{.}{\mathrm{E}}}_{\mathrm{w}\mathrm{a}\mathrm{t};\mathrm{i}\mathrm{n}})={\stackrel{.}{\mathrm{E}}}_{\mathrm{D};\mathrm{c}\mathrm{o}\mathrm{n}\mathrm{d}}$ | ${\stackrel{.}{\mathrm{C}}}_{\mathrm{w}\mathrm{a}\mathrm{t};\mathrm{o}\mathrm{u}\mathrm{t}}+{\stackrel{.}{\mathrm{C}}}_{\mathrm{o}\mathrm{u}\mathrm{t}}={\stackrel{.}{\mathrm{C}}}_{\mathrm{i}\mathrm{n}}+{\stackrel{.}{\mathrm{C}}}_{\mathrm{w}\mathrm{a}\mathrm{t};\mathrm{i}\mathrm{n}}+{\stackrel{.}{\mathrm{Z}}}_{\mathrm{c}\mathrm{o}\mathrm{n}\mathrm{d}}$ | |

IHX | $\mathsf{\epsilon}=\frac{{\mathrm{T}}_{\mathrm{cold};\mathrm{out}}{-\mathrm{T}}_{\mathrm{cold};\mathrm{in}}}{{\mathrm{T}}_{\mathrm{hot};\mathrm{in}}{-\mathrm{T}}_{\mathrm{cold};\mathrm{in}}}$ | $({\stackrel{.}{\mathrm{E}}}_{\mathrm{h}\mathrm{o}\mathrm{t};\mathrm{i}\mathrm{n}}-{\stackrel{.}{\mathrm{E}}}_{\mathrm{h}\mathrm{o}\mathrm{t};\mathrm{o}\mathrm{u}\mathrm{t}})-({\stackrel{.}{\mathrm{E}}}_{\mathrm{c}\mathrm{o}\mathrm{l}\mathrm{d};\mathrm{o}\mathrm{u}\mathrm{t}}-{\stackrel{.}{\mathrm{E}}}_{\mathrm{c}\mathrm{o}\mathrm{l}\mathrm{d};\mathrm{i}\mathrm{n}})={\stackrel{.}{\mathrm{E}}}_{\mathrm{D};\mathrm{I}\mathrm{H}\mathrm{X}}$ | ${\stackrel{.}{\mathrm{C}}}_{\mathrm{c}\mathrm{o}\mathrm{l}\mathrm{d};\mathrm{o}\mathrm{u}\mathrm{t}}+{\stackrel{.}{\mathrm{C}}}_{\mathrm{h}\mathrm{o}\mathrm{t};\mathrm{o}\mathrm{u}\mathrm{t}}={\stackrel{.}{\mathrm{C}}}_{\mathrm{c}\mathrm{o}\mathrm{l}\mathrm{d};\mathrm{i}\mathrm{n}}+{\stackrel{.}{\mathrm{C}}}_{\mathrm{h}\mathrm{o}\mathrm{t};\mathrm{i}\mathrm{n}}+{\stackrel{.}{\mathrm{Z}}}_{\mathrm{I}\mathrm{H}\mathrm{X}}$ | |

TEV | ${\mathrm{h}}_{\mathrm{in}}{=\mathrm{h}}_{\mathrm{out}}$ | ${\stackrel{.}{\mathrm{E}}}_{\mathrm{i}\mathrm{n}}-{\stackrel{.}{\mathrm{E}}}_{\mathrm{o}\mathrm{u}\mathrm{t}}={\stackrel{.}{\mathrm{E}}}_{\mathrm{D};\mathrm{T}\mathrm{E}\mathrm{V}}$ | ${\stackrel{.}{\mathrm{C}}}_{\mathrm{o}\mathrm{u}\mathrm{t}}={\stackrel{.}{\mathrm{C}}}_{\mathrm{i}\mathrm{n}}+{\stackrel{.}{\mathrm{Z}}}_{\mathrm{T}\mathrm{E}\mathrm{V}}$ | |

Evaporator | ${\stackrel{.}{\mathrm{Q}}}_{\mathrm{e}\mathrm{v}\mathrm{a}\mathrm{p}}={\stackrel{.}{\mathrm{m}}}_{\mathrm{r}\mathrm{e}\mathrm{f}}{({\mathrm{h}}_{\mathrm{o}\mathrm{u}\mathrm{t}}-{\mathrm{h}}_{\mathrm{i}\mathrm{n}})}_{\mathrm{e}\mathrm{v}\mathrm{a}\mathrm{p}}$ | $({\stackrel{.}{\mathrm{E}}}_{\mathrm{w}\mathrm{g}\mathrm{m};\mathrm{i}\mathrm{n}}-{\stackrel{.}{\mathrm{E}}}_{\mathrm{w}\mathrm{g}\mathrm{m};\mathrm{o}\mathrm{u}\mathrm{t}})-({\stackrel{.}{\mathrm{E}}}_{\mathrm{o}\mathrm{u}\mathrm{t}}-{\stackrel{.}{\mathrm{E}}}_{\mathrm{i}\mathrm{n}})={\stackrel{.}{\mathrm{E}}}_{\mathrm{D};\mathrm{e}\mathrm{v}\mathrm{a}\mathrm{p}}$ | ${\stackrel{.}{\mathrm{C}}}_{\mathrm{o}\mathrm{u}\mathrm{t}}+{\stackrel{.}{\mathrm{C}}}_{\mathrm{w}\mathrm{g}\mathrm{m};\mathrm{o}\mathrm{u}\mathrm{t}}={\stackrel{.}{\mathrm{C}}}_{\mathrm{i}\mathrm{n}}+{\stackrel{.}{\mathrm{C}}}_{\mathrm{w}\mathrm{g}\mathrm{m};\mathrm{i}\mathrm{n}}+{\stackrel{.}{\mathrm{Z}}}_{\mathrm{e}\mathrm{v}\mathrm{a}\mathrm{p}}$ |

Component | Capital Investment Cost ($) |
---|---|

Compressor | 751.11 |

Condenser | 144.52 |

TEV | 34.16 |

Evaporator | 98.37 |

IHX | 98.37 |

Parameter | Description | Unit | Value |
---|---|---|---|

${\mathrm{i}}_{\mathrm{r}}$ | Interest rate ^{1} | % | 10 |

$\mathrm{n}$ | Lifetime | year | 15 |

${\mathrm{t}}_{\mathrm{ope}}$ | Annual operating time | h | 4000 |

$\mathsf{\phi}$ | Operation and maintenance cost factor ^{2} | % | 1.06 |

Item | R134a BRC | R1234ze(E) BRC | R1234ze(E) IHXC |
---|---|---|---|

Refrigerant charge, kg | 0.52 | 0.5 | 0.63 |

Unit weight, kg | 115 | 115 | 120 |

Annual refrigerant leakage ^{1,2}, % | 4 | 4 | 4.4 |

EOL leakage ^{1,2}, % | 15 | 15 | 17 |

Lifetime ^{1}, year | 15 | 15 | 15 |

Equipment manufacturing ^{3}, kgCO_{2eq} | 409 | 409 | 450 |

Nominal cooling capacity, kW | 3.0 | 3.0 | 3.5 |

Refrigerant | Configuration | Evaporation Temperature (°C) | Suction Pressure (kPa) | Discharge Pressure (kPa) | Superheating (K) |
---|---|---|---|---|---|

R1234ze(E) | BRC | 4 | 152.2 | 672.3 | 4.89 |

9 | 189.9 | 679.2 | 5.14 | ||

14 | 254.3 | 686.5 | 5.39 | ||

R1234ze(E) | IHXC | 4 | 165.7 | 680.2 | 5.28 |

9 | 202.4 | 696.4 | 5.09 | ||

14 | 267.1 | 701.1 | 5.37 | ||

R134a | BRC | 4 | 226.1 | 883.8 | 5.54 |

9 | 299.2 | 893.6 | 5.92 | ||

14 | 370.9 | 911.1 | 5.43 |

**Table 9.**Results of the performance parameters of each refrigerant for the two operating cycles of the installation.

Refrigerant | Configuration | Evaporation Temperature Operational (°C) | Compression Power (kW) | COP | $\mathsf{\psi}$ (%) | TCR ($/h) | SLCCP (kgCO _{2eq}/kWh) |
---|---|---|---|---|---|---|---|

R134a | BRC | 4 | 0.883 | 3.165 | 29.96 | 0.07667 | 63.64 |

9 | 0.835 | 3.544 | 34.65 | 0.06228 | 59.45 | ||

14 | 0.798 | 3.871 | 38.69 | 0.05403 | 57.46 | ||

IHXC | 4 | 0.859 | 3.306 | 38.67 | 0.08784 | 62.35 | |

9 | 0.823 | 3.622 | 40.28 | 0.07145 | 59.72 | ||

14 | 0.779 | 4.049 | 42.99 | 0.07148 | 60.11 | ||

R1234ze(E) | BRC | 4 | 0.909 | 3.064 | 28.17 | 0.08744 | 58.83 |

9 | 0.867 | 3.359 | 29.52 | 0.07406 | 59.87 | ||

14 | 0.841 | 3.726 | 33.80 | 0.06405 | 54.72 | ||

IHXC | 4 | 0.872 | 3.155 | 32.95 | 0.09726 | 57.32 | |

9 | 0.824 | 3.493 | 35.19 | 0.09093 | 54.47 | ||

14 | 0.793 | 3.849 | 36.88 | 0.08053 | 50.7 |

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**MDPI and ACS Style**

Méndez-Méndez, D.; Pérez-García, V.; Belman-Flores, J.M.; Riesco-Ávila, J.M.; Barroso-Maldonado, J.M.
Internal Heat Exchanger Influence in Operational Cost and Environmental Impact of an Experimental Installation Using Low GWP Refrigerant for HVAC Conditions. *Sustainability* **2022**, *14*, 6008.
https://doi.org/10.3390/su14106008

**AMA Style**

Méndez-Méndez D, Pérez-García V, Belman-Flores JM, Riesco-Ávila JM, Barroso-Maldonado JM.
Internal Heat Exchanger Influence in Operational Cost and Environmental Impact of an Experimental Installation Using Low GWP Refrigerant for HVAC Conditions. *Sustainability*. 2022; 14(10):6008.
https://doi.org/10.3390/su14106008

**Chicago/Turabian Style**

Méndez-Méndez, Dario, Vicente Pérez-García, Juan M. Belman-Flores, José M. Riesco-Ávila, and Juan M. Barroso-Maldonado.
2022. "Internal Heat Exchanger Influence in Operational Cost and Environmental Impact of an Experimental Installation Using Low GWP Refrigerant for HVAC Conditions" *Sustainability* 14, no. 10: 6008.
https://doi.org/10.3390/su14106008