BR102020018428A2 - System for reusing the thermal energy of the exhaust gases of a vehicle for cooling or air conditioning - Google Patents

Abstract

A system for reusing the thermal energy of the exhaust gases of a vehicle for cargo cooling or air conditioning of the vehicle's interior is described. More specifically, it comprises a system that uses the thermal energy rejected in the vehicle's exhaust to convert it into kinetic energy for the generation of refrigerant vapor, eliminating the need for coupling to the vehicle's axle or the need for an additional engine to provide cooling of loads or air conditioning inside the vehicle, being provided with means to aspirate, compress the refrigerant vapor, condense the vapor and reduce the pressure and temperature of the refrigerant liquid and control its flow, in such a way as to allow the passage of only the necessary instantaneous flow.

Description

SYSTEM FOR REUSE OF THE THERMAL ENERGY OF GASES FROM THE DISCHARGE OF A VEHICLE FOR REFRIGERATION OR CLIMATIZATION FIELD OF THE INVENTION

[01] The present invention patent describes a system for reusing the thermal energy of the exhaust gases of a vehicle for refrigeration of loads or air conditioning of the interior of the vehicle. More specifically, it comprises a system that uses the thermal energy rejected in the vehicle's exhaust to convert it into kinetic energy for the generation of refrigerant vapor, eliminating the need for coupling to the vehicle's axle or the need for an additional engine to provide cooling of loads or vehicle interior air conditioning.

BACKGROUND OF THE INVENTION

[02] In the transport of cold loads, perishable foods need to arrive at their destination with their characteristics close to those they had at the time they were produced or harvested [COYLE, W., HALL, W., BALLENGER, N., Transportation technology and the rising share of the U.S. perishable food trade, In: U.S. Department of Agriculture. Changing Structure of Global Food Consumption and Trade, 2001.] . The demand for this stage of the cold chain can arise from the simple displacement of cargo from producers located close to the final consumer, to complex intercontinental transport operations, involving the most varied modes, such as land, water and air [BOGATAJ, M., BOGATAJ, L., VODOPIVEC, R., Stability of perishable goods in cold logistics chains, International Journal of Production Economics, 93-94, pp.345-356, 2005.] and [SEABURY, Base de Dados Logísticas, available at: http://www.seaburygroup.com/management-consulting/cargo-logistics, 2007. Accessed: 05/05/2019.] .

[03] The greatest demand for fuel is in the transport of frozen cargo, which is related to perishable cargo. There is also demand related to air-conditioned transport for people, such as air conditioning for buses, chemicals, vaccines and even organs intended for surgical procedures [ABIAF, ASSOCIAÇÃO BRASILEIRA DA INDÚSTRIA DE ARMAZENAGEM FRIGORIFICADA, Technical handout: frozen and chilled foods, 2008.] .

[04] The transport of refrigerated cargo implies an increase of about 50% in freight costs compared to non-refrigerated cargo and part of this additional value is due to the equipment used for refrigeration [ZANOTTI, refrigeration: https:/ /zanottirefrigeracao.com.br/blog/transportadora-de-cargas-refrigeradas-como-funciona/ . Accessed on 07/31/2020] .

[05] The state of the art describes equipment for refrigeration of cargo compartments that basically comprise a compressor associated with an electric motor and/or a combustion engine, and have the same working principle as car air conditioning systems, but with high power, necessary for cooling loads. These equipments, however, have a high cost of acquisition and operation, because although some models have hybrid operation (electric-diesel), it still needs a greater amount of fuel to keep the load refrigerated. Also, the necessary coupling of the compressor shaft to the truck shaft makes the required power much greater, directly reflecting on fuel consumption.

[06] The integration of cargo cooling systems with the energy rejected by the combustion engine is the subject of several studies. It is known that internal combustion engines have low efficiency. Most of the energy provided by the fuel is wasted, with 40% of this energy rejected in the form of heat by the exhaust, 30% through the cooling system (radiators), leaving a small fraction of the total energy to be responsible for the vehicle's displacement. That is, an internal combustion engine is more efficient producing heat than generating useful work (motion) to the vehicle.

[07] Air conditioning consumes considerable power and increases fuel consumption by 3 to 4% when traveling on highways and by up to 10% when traveling in the city [ÇENGEL, Yunus and A.Boles, Michael.Thermodynamics. 2006. Fifth Edition.] . This extra consumption is due to the work that the air conditioning compressor needs to cool the passenger compartment under the necessary conditions. This compressor is driven directly by the car's engine, which consequently needs more fuel for its operation.

[08] Cargo refrigeration equipment has the same working principle as car air conditioning, but with high power. Thus, the activation of the compressor depends on the use of part of the mechanical energy of the motor, which requires greater performance of the motor work and, consequently, greater energy consumption when compared to the transport of conventional loads.

[09] Studies carried out in 1976 showed that the large thermal energy (heat) rejected through the exhaust gases of a truck is sufficient as a source of energy for a cargo refrigeration system [Bellini, Carvalho and Rebouças. TCC, 1976 -University of Brasilia.] . Numerical simulations were based on a water-ammonia refrigeration cycle, and load losses and heat transfers were not analyzed in those studies.

[010] Makiyama [Makiyama, Patrícia Akemi: Improvement of a simulator of water-ammonia absorption refrigeration systems and its application to design a system powered by diesel engine exhaust gas. UNICAMP - Campinas, SP: [s.n.] , 2008] presented the development of a program to simulate a water-ammonia absorption refrigeration system that uses as energy source the exhaust gases of a 123kW diesel engine of maximum power, achieving produce 3720 kg of ice per day. After studying the performance of these operational data, he was also able to dimension and define the main dimensions of the heat exchangers of this refrigeration system.

[011] In recent years, several numerical and experimental studies have been carried out on the temperature control of refrigerated loads. Estrada-Flores and Eddy [ESTRADA-FLORES, S. E., EDDY, A., Thermal performance indicators for refrigerated road vehicles, International Journal of Refrigeration, v. 29, pp. 889-898, 2006.] presented experimental measurements of the temperature profiles found in refrigerated bodies and evaluated the thermal insulation performance.

[012] Although standards such as ABNT NBR 15457 (2007) are available to regulate the constructive aspects of vehicles intended for the transport of loads and there are mathematical models to simulate food cooling, as proposed by Campanone et al. [CAMPANONE, L.A., GINER, S.A., MASCHERONI, R.H., Generalized model for the simulation of food refrigeration: Development and validation of the predictive numerical method, International Journal of Refrigeration, 25, 975-984, 2002.], it is observed that Mathematical models capable of determining the energy consumption of refrigeration systems used in cargo transport are still scarce. It is noteworthy that such models are useful tools to assist in the development of new systems or to compare the financial viability of different modes.

[013] The state of the art describes alternatives that allow the reuse of the thermal energy rejected by the exhaust gases and/or the radiator of the cargo vehicle for use in a system that has the capacity to cool the cargo that the vehicle itself carries.

[014] WO2011162031 describes a vehicle air conditioning device that is capable of quickly heating the interior of a vehicle even immediately after starting, featuring a suction port on the compressor side and an exhaust heat exchanger to provide heat from an engine to a refrigerant under pressure on that side of the compressor where the suction port is located. In an early engine start-up phase, the exhaust heat generated by the engine is supplied by the exhaust heat exchanger to the low-pressure refrigerant on that side of the compressor where the suction port is located, in order to heat the refrigerant. .

[015] Document CN103528260 describes an air conditioning system for automobiles that allows waste heat from exhaust gases to be used. The automobile air conditioning system includes, but is not limited to, a reactor, a condenser, a throttling pressure limiting valve, an evaporator, an absorber, a concentrated solution flow controller, a vapor and liquid separator, and a steam pressurizer, where the reactor collects waste heat from the exhaust gases to generate steam, the condenser cools a liquefied substance generated by the high pressure steam, the throttling pressure limiting valve is used to control the vaporization rate of the substance liquefied substance and maintain the pressure of the liquefied substance, the evaporator is used to perform secondary vaporization on the liquefied substance and absorb heat, so as to allow the liquefied substance to be converted into steam and water at normal temperature, and the absorber absorbs the steam and the water at normal temperature and maintains the evaporator vacuum.

[016] The document FR2950424 describes an equipment that has a reversible air conditioning circuit in which refrigerant circulates. The air conditioning circuit has an evaporator, a compressor, a condenser, an air pressure regulator and a regenerator. An additional heat exchange unit performs the heat exchange with exhaust gases. The exchange unit comprises a calorie storage unit located between the regenerator and a valve. The exchange unit has a cold energy storage unit located between a low temperature radiator and the valve.

[017] The document EP1574698 describes an exhaust heat recovery system for a vehicle with good energy conversion efficiency. A refrigerant is supplied from a vapor-compression-type refrigeration cycle to a boiler that performs heating by the exhaust heat of a vehicle engine. An expander is driven by the coolant heated by the boiler to generate energy, and a generator generates electrical energy. The refrigerant expanded by the expander is returned to the refrigeration cycle and cooled by a cooler in the refrigeration cycle.

[018] In spite of the solutions described in the state of the art, the application of the vapor compression refrigeration cycle, used in air conditioning systems and refrigerators, for refrigeration of loads or air conditioning of vehicles, from the reuse of gases of the vehicle's engine, constitutes an innovative alternative, considering the need to be properly dimensioned, provided with means to aspirate, compress the refrigerant vapor, condense the vapor and reduce the pressure and temperature of the refrigerant liquid and control its flow, in order to allow the passage of only the necessary instantaneous flow.

SUMMARY

[019] The invention describes a system for reusing the thermal energy of the exhaust gases of a vehicle for refrigeration or air conditioning that can be applied in trucks for transporting refrigerated cargo, bus air conditioning, container refrigeration in maritime transport (using the hot gases from the engine on the vessel), among others, to replace the current refrigeration equipment in cold rooms and air conditioning.

[020] The invention describes a system for reusing the thermal energy of the exhaust gases of a vehicle for cooling or air conditioning that has no additional cost in fuel for operation by working with the thermal energy wasted by the vehicle's engine.

[021] The invention describes a system for reusing the thermal energy of the exhaust gases of a vehicle for cooling or air conditioning that reduces the emission of CO2 in the atmosphere, compared to vehicle refrigeration equipment that requires an additional diesel engine.

[022] The invention describes a system for reusing the thermal energy of the exhaust gases of a vehicle for refrigeration or air conditioning that dispenses with the need for short-term maintenance, such as refueling and oil changes.

[023] The invention describes a system for reusing the thermal energy of the exhaust gases of a vehicle for cooling or air conditioning that eliminates the coupling to the vehicle axle or the need for an additional engine.

[024] The invention describes a system for reusing the thermal energy of the exhaust gases of a vehicle for cooling or air conditioning that uses multiple stages to return the fluid to the steam generation unit, allowing preheating and the use of gravity to fluid re-entry, eliminating high pressure pumps.

[025] The invention describes a system for reusing the thermal energy of the exhaust gases of a vehicle for refrigeration or air conditioning that can be developed in different powers, from 100 Watts to equipment for transporting frozen loads (up to 11,000 Watts) .

BRIEF DESCRIPTION OF THE FIGURES

[026] Figure 1 presents the schematic representation of the system for reusing the thermal energy of the exhaust gases of a vehicle for refrigeration or air conditioning, object of the present invention, showing the interrelated operating units.

[027] Figure 2 shows the Compression and Pumping Unit (UCB) in detail.

DETAILED DESCRIPTION OF THE INVENTION

[028] The system for reusing the thermal energy of the exhaust gases of a vehicle for refrigeration or air conditioning, object of the present invention patent, comprises a set of interrelated operational units that basically includes a Refrigeration Unit (RU) with principle similar to compression refrigeration equipment, called Refrigeration Unit (RU) that receives the compressed refrigerant fluid from a Compression and Pumping Unit (UCB) fed by a Steam Generating Unit (UGV) that transfers the thermal energy from a heat source (such as exhaust gases) to the refrigerant.

[029] The Steam Generating Unit (UGV) is responsible for transferring the thermal energy from the exhaust gases (or from a heat source) to the refrigerant fluid.

[030] In the Steam Generating Unit (UGV), the hot gases (g) collected from a heat source (Fc) are directed to a heat exchanger (10), preferably of the cross flow type, where said hot gases (g ) pass through the finned tubes through which a refrigerant fluid, such as R141b, circulates, so that part of the heat from the gases (g) is transferred to the fins of the heat exchanger (10) which, in turn, transfer this heat (g ) for the piping filled with the refrigerant fluid for steam generation, the waste heat being released by an outlet (Sc).

[031] The refrigerant that circulates in the finned tubes of the heat exchanger (10) is moved to the Steam Generation Unit (UGV) by means of a pump actuated by a motor (not shown).

[032] The saturated steam (vs) generated in the Steam Generation Unit (UGV) is directed through a main pipe (11) to the Compression and Pumping Unit (UCB) and to a secondary pipe (12) connected to the Unit of Vapor Recovery (URV).

[033] The saturated steam (vs) received from the Steam Generating Unit (UGV) through the main pipe (11) is directed to the Compression and Pumping Unit (UCB) which performs the mechanical compression of the refrigerant fluid through a set of cylinders pumping units (41) and (41) opposite that carry out the admission, compression and pumping of the refrigerant fluid through the steam (vs) received by the main pipe (11) and which enters a primary driving cylinder (40).

[034] The control of the primary cylinder (40) is achieved by the synchronized actuation of four solenoid valves, two in open position and two in closed position, whose positions alternate synchronously, opening and closing in pairs. As shown in figure 2, valves vs2 and vs3 are responsible for the entry of high pressure steam into the chambers of the main cylinder (40), while valves vs1 and vs4, when open, release steam (vs) to the condenser ( 50) of the Refrigeration Unit (UR), transforming the alternating movements caused by the secondary cylinders (41) and (41') in a single flow direction for the refrigerant fluid, allowing only the admission of saturated vapor (vs) at low pressure in the primary cylinder (40) and the expulsion of the compressed fluid to the condenser (50) of the Refrigeration Unit (UR), within the conditions of pressure, flow and temperature, allowing to electronically automate the pressurized steam inlets and outlets and remotely control the equipment.

[035] When valves vs2 and vs4 are open and valves vs1 and vs3 are closed, high pressure steam (vs) enters the primary cylinder (40) through valve vs2, displacing the piston of said primary cylinder (40) to the right, and the open valve vs4 removes the mass of steam contained in the left part of the cylinder (40) and transfers it to the Steam Condensing Unit (VCU). When the valve opening sequence is reversed, that is, valves vs2 and vs4 closed and valves vs1 and vs3 open, the pressurized steam received from the Steam Generating Unit (UGV) enters through valve vs3 and valve vs1 transfers the mass of steam to the Condensing Unit (UCV).

[036] The compressed refrigerant fluid enters the condenser (50) and condenses, losing heat to the environment until it becomes saturated liquid or compressed liquid, if there is a greater loss of heat to the environment. After passing through the expansion valve (60), the refrigerant fluid operates in a low pressure environment, which causes it to evaporate (70), absorbing heat from the external environment that is cooled, configuring a common cycle of refrigeration by compression. . After evaporation, the steam (vs) returns to the Compression and Pumping Unit (UCB) to be directed to the Steam Compression Unit (UCV), where it will be compressed again and expelled to the evaporator (70), repeating the cycle of refrigeration.

[037] For an equivalent cooling capacity of 100 Watts, the refrigerant gas must enter the condenser at a pressure of 1889.74 kPa (19.27 kgF/cm2) and at a mass rate of 0.00103 kg/s (0 .061913 kg/min). In this process, the fluid condenses below 65°C, losing heat to the environment until it becomes a saturated liquid, and if there is a greater loss of heat to the environment, it becomes a compressed liquid.

[038] After passing through the expansion valve (60), the refrigerant gas operates in a low pressure environment, which causes it to evaporate, absorbing heat from the external environment that is cooled. In this second stage, the fluid leaves the system with a pressure of 200.74 kPa (2.046 kgf/cm2), in the vapor phase.

[039] The Vapor Condensing Unit (UCV) has a radiator (20) that condenses the saturated vapor (vs), so that the saturated liquid (ls) is discharged by gravity to the Vapor Recovery Unit (URV) where said fluid (ls) is preheated before returning to the Steam Generating Unit (UGV).

[040] For the preheating of the saturated liquid (ls), the Vapor Recovery Unit (URV) presents internally to the secondary pipe (12) an upper reservoir (30) that receives the saturated liquid (ls) from the Condensing Unit of Vapor (UCV) through a pipe (13) with a pneumatic solenoid actuation valve (v1) and a lower reservoir (31) connected to the upper reservoir (30) by a pipe (13) equipped with a pneumatic solenoid actuation valve (v2), the lower portion of the lower reservoir (31) having a pipe (13) with a pneumatic solenoid actuating valve (v3) that forwards the fluid (ls) to the Steam Generation Unit (UGV).

[041] In this way, the saturated liquid (ls) released in the Vapor Condensing Unit (UCV) is discharged by gravity to the upper reservoir (30) of the Vapor Recovery Unit (URV). When the upper reservoir (30) is completely filled, the pneumatic valve (v1) is closed, interrupting the flow of liquid (ls) coming from the Steam Condensing Unit (UCV), and the intermediate pneumatic valve (v2) arranged between the upper reservoir (30) and the lower reservoir (31) are opened, draining the fluid (ls) to the lower reservoir (31) where the saturated liquid (ls) is mixed with the saturated vapor (vs) deposited in the lower reservoir (31), raising the temperature of the saturated liquid (ls) to about 115°C. Then the lower pneumatic valve (v3) is opened, draining the preheated saturated liquid (ls) by gravity to the Steam Generation Unit (UGV).

[042] Tests were performed to design the components of the thermal energy reuse system object of the present invention. For example, for an equivalent cooling capacity of 100 Watts and for a mass demand of 0.00103 kg/s (0.061913 kg/min), in the vapor phase at a pressure of 1889.74 kPa (19.27 kgF /cm2), secondary pistons (41) of common dimensions on the market were adopted, with a diameter of 100mm and a total stroke of 180mm.

[043] Thus, the volume of the secondary cylinder (41) and (41') is calculated through Equation 1:

[044] Volume = (pi.D2/4)*L,

[045] Where D=diameter and L=stroke

[046] The volume of the secondary pumping cylinders (41) and (41') is 0.001413716m3. This is the space that will be filled by the low pressure refrigerant gas when it returns from the evaporator (70).

[047] Knowing the volume of the secondary cylinder (41) and (41') and knowing the inlet conditions of the refrigerant gas vapor required for 100W refrigeration, it is possible to determine the total mass of the steam inside these secondary cylinders (41) and (41') through Equation 2:

[048] Mass= p[rô] .V

[049] Where p[rô] is the refrigerant gas vapor density equal to 10.04 kg/m3 at the evaporator outlet conditions (T = -10°C; Vv = 0.0996 m3/kg).

[050] Therefore, the mass of refrigerant vapor inside the cylinder when it is completely filled is m = 10.04 x 0.0014137 = 0.0141937 kg.

[051] Knowing the internal volume of the secondary cylinders and the respective mass of steam contained within them, it is possible to determine the ideal closing time of the cylinders for the pumping of the fluid to occur at the mass flow required for cooling of 100 Watts through Equation 3:

[052] Equation 3: t = (required mass flow rate)/[60x (cylinder mass)]

[053] That is, to pump the mass of refrigerant gas at a rate of 0.061913 kg/min, the cylinders need to complete their stroke in a time of 13.75 seconds.

[054] With the inlet pressure in the secondary cylinder of 200.74kPa (2.046kgf/cm2), and the pressure needed to expel the fluid of 1889.74kPa (19.27kgf/cm2), the force to be performed on the rod for its displacement is calculated through Equation 4.

[055] Equation 4: Force = Pressure x Area

[056] Strength = (1889.74 - 200.74) x [(pi x D2)/4]

[057] Force = 13.26 kN

[058] The force required to reach the minimum pumping pressure is 13.26 kN. Therefore, the primary (drive) cylinder (40) must produce work with a force above this value in order for the system to operate regularly at 100 Watts of capacity.

[059] To calculate the mass of steam required for the main cylinder (40) to complete its total opening or closing cycle, the internal volume of the main cylinder is calculated through Equation 5.

[060] Equation 5: V = pi x (D2/4).L

[061] Where D=cylinder diameter, L=piston stroke, Area=pi x (D2/4)

[062] The mass of steam that occupies the primary cylinder (40) is calculated through Equation 6:

[063] Equation 6: m = V x p[rô]

[064] Where V=volume, p[rô] = 83.89 kg/m3 (T=150°C - saturated steam)

[065] The mass of refrigerant gas vapor that fills the primary cylinder (40) is 0.179717 kg. This mass needs to fill the entire volume of the cylinder in a time of t=13.75 seconds for optimal operation. Therefore, the mass flow rate of the refrigerant gas in the system is calculated by Equation 7.

[066] Equation 7: m= m x 60/t

[067] Therefore, the mass flow rate of saturated vapor of refrigerant gas at a temperature of T=150°C is 0.01306 kg/s.

Claims (2)

SYSTEM FOR REUSE OF THE THERMAL ENERGY OF GASES FROM THE DISCHARGE OF A VEHICLE FOR REFRIGERATION OR CLIMATIZATION, characterized by comprising:

• a) a Steam Generating Unit (UGV) equipped with a heat exchanger (10) where the hot gases (g) collected from a heat source (Fc) perform thermal exchange with the refrigerant fluid to generate steam (vs);
• b) a Compression and Pumping Unit (UCB) connected to the Steam Generation Unit (UGV) through a main pipe (11) that directs the saturated steam (vs) to a primary driving cylinder (40) equipped with pumping cylinders (41) and (41') opposite, said prime mover (40) controlled by the synchronized actuation of two pairs of solenoid valves (vs1 and vs4) and (vs2 and vs3) that synchronously alternate opening and closing, the valves vs2 and vs3 responsible for the entry of high pressure steam (vs) to the chambers of the main cylinder (40) and valves vs1 and vs4 releasing the steam (vs) to the condenser (50) of the Refrigeration Unit (UR) and for the Condensing Unit (UCV);
• c) a Refrigeration Unit (RU) that receives the compressed refrigerant fluid that enters the condenser (50), passes through the expansion valve (60) and through the evaporator (70), returning the steam (vs) to the Compression Unit and Pumping (UCB) to be directed to the Vapor Compression Unit (UCV), where it will be compressed again and expelled to the evaporator (70), repeating the refrigeration cycle;
• d) a Condensing Vapor Unit (UCV) that has a radiator (20) that condenses the saturated vapor (vs) and discharges the saturated liquid (ls) by gravity to the Vapor Recovery Unit (URV);
• e) a Steam Recovery Unit (URV) that receives the fluid (ls) from the Steam Condensing Unit (UCV) for preheating, internally presenting to the secondary piping (12) that connects with the Steam Generating Unit (UGV) an upper reservoir (30) that receives the saturated liquid (ls) from the Condensing Vapor Unit (UCV) through a pipeline (13) with a pneumatic solenoid actuated valve (v1) and a lower reservoir (31) interconnected to the upper reservoir (30) by a pipe (13) equipped with a pneumatic solenoid actuation valve (v2), the lower portion of the lower reservoir (31) having a pipe (13) with a pneumatic solenoid actuation valve (v3) that forwards the fluid (ls) mixed with the saturated steam (vs) deposited in the lower reservoir (31) to the Steam Generation Unit (UGV).

SYSTEM FOR REUSE OF THE THERMAL ENERGY OF GASES FROM THE DISCHARGE OF A VEHICLE FOR REFRIGERATION OR CLIMATIZATION, according to claim 1, characterized in that the refrigerant fluid circulating in the heat exchanger (10) is moved to the Steam Generation Unit ( UGV) by means of a pump driven by a motor (not shown).

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