# A Review of Small-Scale Vapor Compression Refrigeration Technologies
## 3 Small-Scale Vapor Compression Refrigeration (VCR) Systems
### Small-Scale Vapor Compression Applications
#### 3.1.1 Electronics Cooling
[51], on the other hand, demonstrated a compact VCR system that is adapted but not integrated into a gaming laptop for supplying cold air to improve its performance. The required cooling capacity was 30 W at 10 \({}^{\circ}\)C evaporating temperature  
Figure 11: Experimental equipment of (**a**) [PERSON] and [PERSON] and (**b**) [PERSON] et al. [46]. and 45 \({}^{\circ}\)C condensing temperature. Isobutane was selected as refrigerant from a theoretical comparison that considered operating pressures, discharge temperature, and volumetric flow, among other properties. All system components were designed for this specific application; a linear reciprocating compressor was constructed and tested in a calorimeter, obtaining a cooling capacity of 34.6 W, for a COP = 2.55, and 42% isentropic efficiency, under the specified operating conditions on a basic cycle mode. For the condenser and evaporator, microchannel heat exchangers were designed and constructed. Finally, the capillary tube was dimensioned according to a methodology proposed by [PERSON] et al. [52]. Figure 12 shows the experimental unit. The telecommunications area is another important application that demands the cooling of electronic components for adequate operation. The need for compact telecom cooling units that may perform as efficient substitutes for thermoelectric coolers and the scarcity of studies in the literature motivated Ribeiro to test a VCR system for this application. The initial work [53] presented a prototype made of a linear oil-free micro compressor, finned tube heat exchangers as condenser and evaporator, and a capillary tube as an expansion device, operating with R134a. The overall dimensions were 528 \(\times\) 127 \(\times\) 96 mm\({}^{3}\) and 3.1 kg weight, and it used 59 g of optimized refrigerant mass and a 1.10 m long capillary with 0.518 mm diameter. The cooling capacity and COP evaluation considered both controlled and full piston stroke cases. The controlled stroke produced 72.6 W of cooling capacity, similar to that obtained with the thermoelectric unit. However, the COP was doubled at 1.45. The full stroke test resulted in a larger cooling capacity of 109 W and a lower COP of 1.01. In a second work, [PERSON] [54] proposed a similar experimental apparatus, except that an additional pre-condenser and post-evaporator were added to the system as seen in Figure 13, causing an increase in the dimensions and weight (660 \(\times\) 200 \(\times\) 120 mm\({}^{3}\), and 8 kg). The aim of adding these devices was to partially condense the refrigerant in the pre-condenser and then send it to the post-evaporator, which was a serpentine tube in contact with the compressor, to decrease the shell temperature, permitting its suitable operation in hot climates. Other system components remained unchanged. The tests were carried out with a full piston stroke at 25, 35, and 55 \({}^{\circ}\)C ambient temperatures. The results showed an optimized R134a charge of 138 g and 1.15 m capillary length. Moreover, the vapor compression system demonstrated a COP of 1.09--double that of two thermoelectric cooling units used for comparison, although a thermoelectric unit had higher cooling capacity (150 vs. 120 W). Figure 12: Cooling system developed by [PERSON] et al. [51]. Another application within the field of electronic component cooling is in avionic systems. Unlike other systems, electronic components in aeronautical applications can operate at temperatures as high as 80-120 \({}^{\circ}\)C. However, size and weight minimization is critical, resulting in atypical designs. [PERSON] et al. [55] used a cold plate as evaporator specifically developed for use inside an avionics package. Their use of a fixed-speed linear compressor allowed for the testing of compression ratios between 1.54 and 3.75, and piston displacements between 25 and 90%, obtaining COP values between 1.04 and 5.8 and cooling capacities between 37 and 374 W.  
[PERSON] et al.