**1. Introduction**

Nanorefrigerant was defined to complete the objective of improving thermal performance using little possible fraction of nanoparticles in the base refrigerant. An improved term of refrigerant known as "nanorefrigerant" firstly introduced and experimentally implemented by Wang et al. [1]. The addition of nanoparticles in refrigerant improves the system performance in terms of improvement in flow and pool boiling heat transfer characteristics as well as flowing pool condensation heat transfer [2, 3]. Nowadays, nanorefrigerant and nanolubricant became a great alternate to enhance the performance of cooling cycles in terms of tribology performance, heat mass transfer properties and refrigerant/oil mixture relations [4–7]. Specifically, nanorefrigerant improves the heat transfer coefficient at evaporation and condensation whereas a nanolubricant improves the tribology characteristics which ultimately increase the compressor performance. The expected volume concentration of nanoparticles is calculated using Eq. (1).


**Figure 1.**

*Formation of nanorefrigerant in VCR cycle.*

$$\mathbf{o} = \frac{\frac{m\_p}{\rho\_p}}{\frac{m\_p}{\rho\_p} + \frac{m\_L}{\rho\_L}} \times \mathbf{100} \tag{1}$$

Jwo et al. [8] dispersed 0.1% mass fraction of Al2O3 particles in polyester oil and

reported 2.4% reduction in compressor work. Mahbubul et al. [9, 10] reported

nanoparticles dispersed in R141b. Later, the author observed increment in heat transfer coefficient and pressure drop up to 383 and 181%, respectively using particle volume fraction between 1 and 5% with fixed mass flux of 100 kg/m<sup>2</sup> s. Mahbubul et al. [11] reported large frictional pressure drop of R134a/Al2O3 nanorefrigerant as compared to R113/CuO nanorefrigerant flows inside horizontal

Sun and Yang [13] studied the effect of Alumina-R141b, Cu-R141b, Al-R141b and CuO-R141b with mass fractions 0.1–0.3 wt% in a computer aided test rig on

improved pool boiling heat transfer coefficient in the system but adding surfactant

Mahbubul et al. [17] dispersed Al2O3 in R141b refrigerant for thermal conductivity and viscosity investigation. The author reported that viscosity and thermal conductivity of R141b/Al2O3 nanorefrigerant at 2% volume fraction are 179 and 1.626 times greater than pure refrigerant. Jwo et al. [8] used 0.05–2% weight fraction of Al2O3 particles with R134a and R12, respectively and reported that R134a refrigerant replaces R12, as polyester oil replaces mineral oil. Further, 0.1 wt% fraction of nanoparticles in R134a refrigerant reduced the energy consumption by 2.4% which significantly improved the COP of refrigerator. Kumar and Elansezhian [18] experimentally investigated the effect of R134a/Al2O3/PAG blend on the overall performance of VCR cycle and observed lower energy consumption by 10.32%. Author stated that using nanoparticle in refrigeration system is a cost effective method which improve its COP and length of capillary tube is reduced.

Subramani and Prakash [19] observed 25% less energy consumption and 33% overall COP enhancement in VCR cycle using Al2O3 nanorefrigerant. The freezing capacity of the cycle was also improved. Yusof et al. [20] dispersed 0.2% Al2O3 particles in polyester (POE) lubricant and reported 7% improvement in system COP and 2.1% reduction at compressor energy consumption. Cremaschi et al. [21] studies that alumina nanoparticles did not improve the solubility between refrigerant and lubricant, while addition of nanoparticles had slightly lowered the solubility of

Kedzierski and Gong [22, 23] observed heat transfer improvement between 50 and 275% using 0.5% mass fraction of CuO particles with R134a/RL68H and R134a/ POE blend. Moreover, R134a/RL68H blend shows higher heat transfer enhancement as compared to the R134a/POE blend. In Later study, the author used 2 Vol% fraction of CuO particles in R134a refrigerant and reported nanorefrigerant has higher heat flux. Bartelt et al. [24] dispersed 0.5–1% mass fraction of CuO nanoparticles in R134a/polyester blend in horizontal flow boiling conditions and

at higher concentration corrupted the heat transfer process.

R410a/POE.

**103**

**2.2 Studies related to CuO**

significant increment in thermal conductivity and viscosity with Al2O3

*Effect of Nanoparticles on Performance Characteristics of Refrigeration Cycle*

flow boiling heat transfer in horizontal tube and reported that Cu-R141b nanorefrigerant had the highest heat transfer coefficient as compared to other mixtures. Kedzierski [14] dispersed 1.6% volume fraction of Al2O3 in R134a/POE mixture flows on a horizontal and rough flat surface and found that higher volume fraction of nanoparticles with low average diameter has greater positive effect on heat transfer characteristics of base refrigerant. Further, Kedzierski [15] investigated the effect of Al2O3 nanoparticles on the pool boiling characteristics of R134a/ POE mixture inside the rectangular finned surface and reported that 3.6% nanoparticle volume fraction enhanced the boiling heat transfer performance up to 113%. Tang et al. [16] reported that using δ-Al2O3 with R141b significantly

smooth tube due to higher vapor quality [12].

*DOI: http://dx.doi.org/10.5772/intechopen.89236*

where, ø is the volume fraction in percentage, *ρ<sup>p</sup>* and *ρ<sup>L</sup>* are the density of nanoparticles and density of the lubricant respectively; and *mp* and *mL* are the masses of nanoparticles and lubricants respectively. The formation of nanorefrigerant is possible as shown in **Figure 1**.

The present chapter aims to define the mechanism that steers towards improvement in overall VCR cycle performance using nanolubricants and nanorefrigerants. The authors' hope that this paper will be useful to define the research gaps and understands the contribution of nanorefrigerants and nanolubricants in refrigeration cycle.
