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R407H, drop-in de reducido GWP del R404A, evaluación experimental

Durante estos últimos meses en el Grupo de Ingeniería Térmica (www.git.uji.es) de la Universitat Jaume I hemos estado estudiando el refrigerante R407H (GWP=1378) como sustituto drop-in del R404A (GWP=3945) en sistemas centralizados de expansión directa a baja temperatura. En concreto, hemos realizado medidas de consumo energético en nuestro pequeño supermercado en condiciones de laboratorio (25ºC, 60% HR) manteniendo el producto en una isla de congelados a -20ºC con temperaturas de condensación de 25, 35 y 45ºC, y hemos realizado ensayos energéticos durante el proceso de recarga parcial del sistema de R404A con R407H (Figura 1).

Respecto a las pruebas de recarga parcial (top-up test), realizamos recargas parciales del sistema con R404A con R407H, en proporciones de recarga en masa del 10, 20 y 30%. Solo para una proporción de R407H del 30% observamos incrementos del COP de hasta un 4.9% acompañados de un incremento en temperatura de descarga de 6.3K (Figura 2).

Respecto a la evaluación energética, hemos observado que el uso del R407H en lugar del R404A es favorable, ya que el uso permite reducir el consumo del compresor hasta en un 7.7% y del sistema en conjunto hasta en un 4%. Sin embargo, hay que destacar que medimos un incremento en la temperatura de descarga del compresor de hasta 13.8K (Figura 3).

En conclusión, podemos decir que el R407H es un buen alternativo al R404A, ya que ofrece una reducción del GWP del 65% y reducciones del consumo energético de compresor de hasta un 7.7%.

R404A/507 in MT and LT applications

A low GWP and Low Cost service solution for R404A/507 in MT and LT applications

The European F-Gas regulation EU517/2014 is upon us. Effective since 2015, the regulation is entering a new phase of accelerated phasedown of the HFC consumption within the EU28. Compared to the baseline year of 2015, a reduction step of 37% of available quota is set for January 2018. Even in 2017, the requirement that imported pre-charged equipment consumes quota will add pressure on available quota. Owners and operators of existing installations need to find urgently cost effective solutions to maintain their equipment and cooling service.

Who is at risk?

Industry studies have shown that the largest burden on the F-gas industry to reduce its CO₂ footprint will be carried by the commercial refrigeration sector. Especially impacted are systems running on high GWP refrigerants such as R404A / R507. According to EPEE's Gapometer study, 50% of existing R404A systems should be replaced or converted to a lower GWP refrigerant by January 2018 to meet this requirement.
This raises a huge challenge for our industry. Indeed, the race to retrofit these high GWP gases in commercial systems puts even more short-term pressure on quota availability. This fact, combined with further step-downs in F-gas quota means that the right choice of refrigerant is critical for initial retrofit and future service.

Choosing a Low GWP and Low Cost retrofit refrigerant - a 3-component choice

Cost Component 1: Lower the GWP

The F-gas cap and phasedown schedule for CO₂ equivalent quota will inevitably put increasing pricing pressure on each tonne of CO₂ required by the EU market. It is therefore essential that plant owners and operators get to the lowest GWP levels for an A1 refrigerant in their commercial refrigeration installations. Any refrigerant with a GWP greater than 1500 will see rapidly increasing cost pressure and may even require a second retrofit to lower GWPs in order to meet the cap and phasedown schedule.
R407H is an A1 classified refrigerant with a GWP <1500

Cost Component 2: The molecules

R407H is a mixture of R32 / R125 / R134a. It has been specially developed to enable a low-cost conversion of R404A and R507 systems without the need for expensive HFO components.
We at Daikin believe that the EU refrigeration industry will need HFO based solutions to comply with the F-gas regulation. Indeed, Daikin has a broad portfolio of HFO technologies. However, it is a fact that HFO molecules are more expensive to produce than traditional HFCs. We believe that the industry should only pay for HFOs or even more expensive solutions when absolutely necessary. For the replacement of most R404A / R507 MT and LT systems, R407H provides equivalent performance to HFO-based technologies with a GWP also below 1500.

Cost Component 3: Ease of retrofit & performance

In most cases, R407H can be used without major changes to existing R404A / R507 systems. R407H can be considered a "drop in" solution for many systems ². Studies have shown that R407H has an improved COP vs other HFO/HFC based replacement refrigerants and better cooling capacity than R404A.
We believe that multiple solutions will be necessary to meet the F-gas Regulation.
HFO based technologies will be a part of those solutions and Daikin's portfolio reflects these technologies.
However, for many A1 refrigeration applications where replacement of R404A / R507 is the greatest challenge for users and contractors, R407H can meet their F-gas needs by offering:

Lower GWP	<1500
Performance	equivalent or higher than R404A/R507
Lower cost	no need for more expensive HFO based blends
Ease of Retrofit	a drop in solution for many systems

Physical data ³

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		R404A	R507	R407H
Chemical Formula		CHF2CF3 CH3CF3 CH2FCF3	CHF2CF3/ CH3CF3	CH2F2 CHF2CF3/ CH2FCF3
Molar Mass	kg/kmol	97.6	98.86	113.07
Boiling Point at 1.013 bar	°C	-46.2	-46.74	-44.7
Critical Temperature	°C	72.0	70.6	86.5
Critical Pressure	bar	37.29	37.1	48.5
liq. cp 4	kJ/(kgK)	1.542	1.539	1.585
vap. cp 4	kJ/(kgK)	1.221	1.225	1.176
Ratio cp/cv, vap. 4		1.37	1.38	1.36
Spec. density, liq. 4	kg/m³	1044	1048	1111
Spec. density, vap. 4	kg/m³	65.27	68.89	41.86
Enthalpy of vaporization 4	kJ/kg	140.26	136.45	199.02
Explosive limit in air 5	% v/v	N/A	N/A	N/A

² However, R407H cannot be considered a "drop-in" for every system. For example, due to R407H's higher discharge temperature compared to R404A / R507, measures such as liquid injection would need to be considered for discharge temperatures exceeding 80°C.
³ Thermo-physical data calculated by Refprop 9.0
⁴ sat. @ 25°C
⁵ T = 25°C, p= 1.013bar

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