RV Fridge

Recreational vehicles (RV) are designed to be truly self-contained so a refrigerator is an essential appliance. RVs are subject to conditions that make the design of their refrigerators challenging. The main challenges are vehicle vibration, accelerations, the energy required to drive the refrigeration process, and the off-level nature of vehicles. The absorption type refrigerator overcomes most of these design challenges and this is why the absorption refrigerator has been popular since the 1950s.

Following is a block diagram and a simplified drawing of a typical absorption type RV Fridge. The block diagram is a simplification of the fridge cycle which shows the key components combined with the fluid flow within the circuit. The simplified fluids schematic more closely resembles the actual refrigeration cycle so that the reader can draw a connection between the components on their fridge and what is occurring within the cooling unit pressure vessel.

The first absorption refrigeration system was patented by Ferdinand Carre in 1859. This refrigeration system had mechanical pumps and throttling valves which change the pressures in the refrigeration cycle.

The RV Fridge is considered a single pressure absorption refrigeration (SPAR) system because the entire system is at the same total pressure. Because there are no pumps or compressors it is easy to sustain these fridges in an RV as long as propane (LP gas) is available. The SPAR was patented by Baltzar von Platen and Carl Munters in 1923.

The block diagram shows the flow of fluids (Qx) along with the flow direction arrows. Also, the heat input (endothermic process) and heat rejection (exothermic process) for the respective components has been identified. The fluid flow is as follows:

Q1: The yellow line is the holding tank mixture of liquid water, ammonia, and a rust inhibitor.

Q2: The blue line is the weak solution. The weak solution preferably consists of only water and the rust inhibitor as a result of the distillation process.

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Wikipedia