Analysis for the Heat Rejection Calculation for the Compact Condenser Which Rejects Heat from the Refrigerant

Literature review

The literature review gives the highlight of the previous research related to the study of the heat rejection technique for the compact condenser. The analysis focuses on the effectiveness of the compressor, the review on technological developments of the condenser and the increase in the mass flow rate.

Effectiveness

According to the American Society of Mechanical Engineers. (2010), the evolution of the compact condenser within refrigerators has sought to increase the level of efficiency and effectiveness. It is estimated that much of the energy within a refrigerator is consumed by the condenser (Gehin, Zwolinski & Brissaud, 2009). Additionally, the need to increase effectiveness has been raised by the fact that the condenser should be efficient in offering a cooling effect within the refrigerator. The efficiency of the condenser is the measure of how efficiently the decompressed gas within a refrigerator is changed into the liquid based on the pressure and temperature change. Vineyard & Sand, (2018), argued that different approaches might be used in determining the effectiveness of the condenser.

According to Gehin, Zwolinski & Brissaud, (2009), one of the main factors that determine the effectiveness of the condenser is the condenser type. Currently, manufacturers and researchers have come up with different types of condensers. However, three major types are considered to be most effective. The Neverclean condenser is one of the models which has a high level of effectiveness (Hebestreit & Lang, 2016). The above type, the capacitor works when the air is forced over the refrigerant condenser pipes by a fan. According to Hebestreit & Lang, (2016), the fresh air is responsible for the removal of the heat that is generated during the normal working of the fridge. Most of the new automatic defrost refrigerators are currently operated using the Neverclean condenser (Hebestreit & Lang, 2016). The effectiveness of the overhead condenser is also increased by the ability of the condenser to collect dust and other debris within the refrigerator area, a process which also increases the effectiveness of the cooling effect.

The forced air condenser is another type of modern condenser which has highly effective features (Vineyard & Sand, 2018). The efficiency of the above example is based on its ability to have air forced through the condenser coil to increase the level and extent of cooling. The atmosphere within the loop if pushed by a fan and it improves the efficiency of the cooling process for the hot air. The location of the forced air condenser is also an essential factor in the determination of its effectiveness. Usually, the condenser is located below the fridge on the fan situated to one side. The fan pulls air and ejects the hot air to the other side (Hebestreit & Lang, 2016). The warm air that is considered as waste is also passed over the drip pan. The atmosphere is responsible for the defrosting process of the air that has accumulated and become defrosted. Figure 1.0 shown below shows the overall outlay of the condenser about the position of the compressor and the fan within a fridge setup.

Figure 1.0: Condenser, Cut-away view

The third type of condenser that has also been invented with the primary aim of increasing efficiency is the Natural Draft condenser (Hebestreit & Lang, 2016). In recent times, the Natural draft has mainly been used in the manufacture of single door and manual defrost fridges. The model has a condenser that is a draft model and is useful in the disposition of heat that comes from the refrigerator. In most cases, the efficiency is also based on the location of the Natural Draft which is found on the back of the fridge.

The calculation of the effectiveness of the condenser can be approached in different ways. There are several assumptions which have to be put in place when it is necessary to carry out the effectiveness calculations. One of the premises is that the coolant should pose a constant density and heat capacity. Additionally, there should be a continuous linear enthalpy which is distributed over the range of temperature. Final there should be no longitudinal transfers.

The formulae for the calculation of the effectiveness of the condenser is given by

∇x=Th-TxTh-TO+=e-NTU2=e-hpx/me=egx/mcl

Where:

x- distance from the inlet of the coolant

T(x)- the temperature for the coolant

T(o)- the temperature for the coolant at the inlet

NTU- the number of transfer units

m- mass for the coolant

c- heat capacity for the coolant

c- heat transfer coefficient

P- the coolant tube perimeter

G- conductance heat based on the coolant tube

L- the length of the coolant tube

Technology

In their book, Srikhirin, Aphornratana & Chungpaibulpatana, (2011) noted that there had been many developments related to refrigeration condensers in the past. The need to improve the functionality, efficiency, and performance of the refrigerator has increased the efforts of scientist to do more research on the condensation process. There are, however, specific components of the condenser that have changed substantially with the introduction of advanced technology. The diagram represented below shows the actual condenser as it appears within a refrigeration system.

Figure 2.0: Figure 1. Condenser system

The invention of the condensers has been based on the need to reduce the size. The first refrigeration condensers were massive in size and occupied much space. (Talbi & Agnew, 2010) The need to reduce the size mainly focused on the modification of a variable component of the condenser system. One of the major technological development aimed at reducing the size of the condenser was the condensing coil. One of the newest condensing coils in the refrigeration system is the ST condensing series (Talbi & Agnew, 2010). The major improvement that has been enhanced on the coil is the addition of features that ensure that the inflow of air and coolant spray get evenly distributed on the coil. The coil, which was originally invented by the Korean Institute of Industrial Technology has custom made features. The rods used within the coil are galvanized with iron and steel pipes which ensure that the product is durable and effective (Talbi & Agnew, 2010). The manufacturing and production process are also enhanced through stringent measures and laws that ensure its quality and performance.

According to Critoph, (2018), the fan motor and the entire fan section of the condenser has also undergone a lot of technological advancements. The introduction of aluminum fans was one of the breakthroughs in the condenser manufacturing process (Critoph, 2018). Currently, the aluminum fans are always attached to the high-powered motor which is strongly enclosed within a galvanized casing. The dye-type motor is usually mounted on top of the condensers with the aim of ensuring that there is an adequate flow of air within the coil and thus an improvement of the efficiency. The spray assembly and the system for the water distribution within the refrigeration condenser have also undergone immense technological changes. In modern time, the coolant pipes have been selected from materials that are resistant to corrosion. The tubes are also designed with the aim of enhancing even spray. Further, the nozzle of the coolant sprays is also made of ABS materials. The materials are especially important in the prevention of any blockages on the nose even after long hours of operation (Critoph, 2018). The documents also ease the process of maintenance of the condenser.

The introduction of micro-channel tubes which are made from aluminum has also revolutionized the operation of the condenser. The machines are usually fitted with accordion louvered fins which increase the surface ratio (Manske, Reindl & Klein, 2011). The coefficients for heat exchange are always higher based on the need to maintain an equal air velocity. The design of the heat exchangers for the fin has attracted a lot of technological research with the aim of reducing the pressure constraints which is mainly attributable to the C02. In the past two years, refrigeration scientists have been focusing their efforts on arranging microchannel tubes in different circuits to achieve the maximum positive impact (Manske, Reindl & Klein, 2011). Figure 3.0 below shows the simple layout of the new micro-channel aluminum tubes.

Figure 3.0: microchannel heat exchangers

The cooling capacity of the refrigeration system has also been enhanced through other minor changes in the condenser layout. The condenser has been enhanced with heat absorption capabilities which make it to quickly transfer eat across its components. One of the main developments in the above field is the introduction of the electronic cooling system. Within the system, air is used as a significant component in the rejection of heat within the condensing mode. The loss of heat within the condenser is always minimized by having compressed air within the medium (Manske, Reindl & Klein, 2011). The motive of the scientists was to ensure that the air that comes in has a temperature that is as close as possible to the ambient temperature.

Despite the many developments in the entire refrigeration functionality process, there are still many research areas which are under exploration. A lot of technological advancements are still expected in the future.

Increase in the mass flow rate

There has always been a need to develop a standard mass flow rate for the refrigeration system. The correlation is essential in promoting the examination process for a different range of refrigerators. By definition, the mass flow rate is the mass of refrigerant that passes through the coil of a condenser within any given time. The calculation of the mass flow rate always takes place through controlled methods and processes. The use of short tubes in the computation of the flow rate enhances the level of vapor comparisons. The calculation of the mass flow rate can be achieved through a model from a which a formula is used.

M=KA (2gp(Pup-Pdown)

Whereby:

m – mass flow rate

K – orifice constant

A – orifice area

g – gravitational force per unit mass

ρ – fluid density

P – upstream and downstream pressure

According to Gu, Liu, & Li, (2014), there are many studies which have been carried out with the aim of enhancing an understanding of the mass flow characteristics. In the last few years, the reviews on the mass flow characteristics have mainly been focused on the hydrofluorocarbons (HFC) refrigerants (Gu, Liu, & Li, (2014). The above method of study is accomplished through the inclusion of different study methods. Some of the most applicable methods include the equilibrium method and the homogenous frozen method. Based on the above equation, different designers have developed the capacity and ability to determine the mass flow rate of a refrigerant that is passed through a short tube. There, however, has to be an upstream pressure and temperature. The correlations may always be applied to different types of refrigerants.

According to the American Society of Mechanical Engineers (2010), Forced cooling is also a significant method that is always applied to the condensation process. The forced cooling technique is whereby the condensation takes place as the fluid flow through the tube. During the process, a fan is placed next to the machine, and it is allowed to rotate as the fan rotates around the tube. Cool air is generated. The fresh air, after that, enables the process of condensation within the cells. However, the approach of forced cooling is not practiced commercially owing to the increased technology. Apart from being old-fashioned, the plan is time-consuming and less efficient (Gu, Liu, & Li, 2014). The use of conventional cooling methods that are mostly automated has therefore been adopted to replace the traditional cooling approaches. The improved technology has also made the cooling process very efficient and timely. Current refrigeration processes have led to the production of more sustainable refrigerators.

Conclusion

In conclusion, the study has revealed different adaptation of a compact condenser in aiding the performance of a refrigerator. There have been numerous research materials that have explored the effectiveness of the compressor which forms an integral part of the condenser. Some of the significant findings indicate that the compressor’s efficiency depends on factors such as its location, the compressor load and the level of insulation around the compressing tubes to prevent heat loss. There have also been many reviews on the level of technological advancement and growth specifically on the evolution, development, and improvement of the condensers. The study found out that many materials support the fact that technology has been critical in promoting the development of new and more efficient condenser designs and outlooks. Finally, the review has also included much research on the mass flow rate. Most of the studies found out that the mass flow gives the measure of the mass of the refrigerant fluid that flows through the tube within any given time. The fluid mainly serves the function of promoting condensation. However, another researcher also had working evidence of other cooling methods. The most common way, according to the researchers, was the forced cooling approach.

References

American Society of Mechanical Engineers. (2010). Heat pump and refrigeration systems design, analysis, and applications. New York: American Society of Mechanical Engineers.

Critoph, R. E. (2018). Forced convection adsorption cycle with packed bed heat regeneration: Cycle à adsorption à convection forcée Avec régénération thermique du lit fixe. International Journal of Refrigeration, 22(1), 38-46.

Gehin, A., Zwolinski, P., & Brissaud, D. (2009). Integrated design of product lifecycles—The fridge case study. CIRP Journal of Manufacturing Science and Technology, 1(4), 214-220.

Gu, Z., Liu, H., & Li, Y. (2014). Thermal energy recovery of air conditioning system––heat recovery system calculation and phase change materials development. Applied Thermal Engineering, 24(17-18), 2511-2526.

Hebestreit, L., & Lang, A. (2016). U.S. Patent No. 7,100,390. Washington, DC: U.S. Patent and Trademark Office.

Manske, K. A., Reindl, D. T., & Klein, S. A. (2011). Evaporative condenser control in industrial refrigeration systems. International Journal of Refrigeration, 24(7), 676-691.

Srikhirin, P., Aphornratana, S., & Chungpaibulpatana, S. (2011). A review of absorption refrigeration technologies. Renewable and sustainable energy reviews, 5(4), 343-372.

Talbi, M. M., & Agnew, B. (2010). Exergy analysis: an absorption refrigerator using lithium bromide and water as the working fluids. Applied Thermal Engineering, 20(7), 619-630.

Vineyard, E. A., & Sand, J. R. (2018). Fridge of the future: Designing a one-kilowatt-hour/day domestic refrigerator-freezer (No. ORNL/CP-97456; CONF-980815-). Oak Ridge National Lab., TN (United States).