Hot Gas Heater System Yoshiaki TAKANO Teruyuki HOTTA Yasushi YAMANAKA Masahiro SHOJI As a result of recent improvements in engine efficiency, vehicle heater performance has decreased and the demand for auxiliary heat sources is increasing. To help meet this need, we have developed an auxiliary heat system known as the Hot Gas Heater. The Hot Gas Heater uses components common the vehicle airconditioning system that are not used during winter. However, there are some concerns with this system. In this paper we describe our solutions these problems. We reduced gas flow noise through multi-stage pressure reduction, and prevented fogging by adding Anti-Fogging Algorithm and evaporar outlet air temperature control functions the system. As a further benefit, we developed a New Accumular Cycle that transfers the cooling cycle accumular tank the high-pressure side. Key words : Hot Gas Heater, Noise reduction, Fogging, New Accumular Cycle Mollier diagram Liquid Evaporar Accumular Two phase Cooling Heat pump Hot gas Gas Heat exchanger Fig. 1 Hot Gas Heater layout Throttle Performance Power Loss
High pressure (MPa) Eng. Power 1.6kW 2 1 Heat loss.5kw 6ºC Heater ºC Evaporar -2ºC Performance Q 2.kW Water temp. UP.9kW Performance of evaporar 1.1kW Fig. 2 Hot Gas Heater performance Preformance Q (kw) 6 4 2-3 -2-1 Ambient temp. (ºC) 2r/min 15r/min 1r/min Fig. 3 Performance characteristic Throttle (near Conderser) Pressure 2. (MPa).7 Tube ( φ8) [Condition] -1ºC, 15r/min Joint Fig. 4 Multi-stage pressure reduction.4 Heat exchanger
Accumular Oil return hole Noise (dba) 7 6 5 4 Returning amount of oil & liquid refrigerant up Two phase flow of evaporar Liquid Fig. 5 Two phase flow [Condition] -1ºC Multi-stage pressure reduction Two phase flow Two phase Usual method 5 1 15 revolution (r/min) 68dB 54dB (48.5dB) 45dB Fig. 6 Gas flow noise (bench evaluation) Gas Noise (dba) 6 5 4 3 2 1 Background noise [Condition] -1ºC, idle, Diesel wagon Usual method (damping materials) Our method 2 4 6 8 1 Frequency (khz) Fig. 7 Gas flow noise (vehicle) No No Without control Adhesion of water Cooler operation Outlet air Adhesion of water Yes outlet air temp. Windshield temp. Hot gas operation Condensation Generation of fog Inlet air Evaporation of water Inlet air Yes Defogging control Cooling of evaporar Heationg of evaporar Memory of water retention Amount of water retention in eva. = Condensation Evaporation Displacement Water retention in eva. (g) outlet air temp. (ºC) Cooler operation 25 3 2 1 No operation Time (h) Generation of fog Hot gas operation -1-2 -2-1 1 2 3 Windshield temp. (ºC) Presumption of windshield temp. = Ambient temp. + f(water temp, time) Fig. 8 Cause and countermeasure of fogging
T ws [Condition] -1ºC, LA#4, Me1, foot/def, Diesel wagon T ws (ºC) 1-1 Measured value Calculated value 1 2 3 Time (min) Fig. 1 Windshield temperature α α λ T am SPD Fig. 9 Concept of estimating the windshield temperature T WS T a t α 1 T λ = α1 + T α a + T α1 t 1+ + α i α λ t α1 T λ a Driver s seat am am Bypass tube Operation-changing valve Electromagnetic valve Differential pressure valve Heating Cooling Evaporar Expansion valve Tank Check valve Hot gas tank Oil return hole Fig. 11 Hot Gas Heater based on receiver cycle Joint Evaporar Bypass
Accumular Cycle New Accumular Cycle Evaporar Evaporar Accumular tank with tank Orifice (Gas) Orifice Accumular Evaporar (Liquid) Fig. 13 New Accumular Cycle outline Heating Cooling Accumular Cycle New Accumular Cycle out SH Operation changing valve Electromagnetic valve Check valve Differential pressure valve Orifice tube Tank Evaporar [Evap. out SH=ºC] Move accumular tank low-pressure side high-pressure side Indirectly control evap. out SH by controlling comp. out SH Tank Evaporar Evap. out SH isentropic line Fixing tank condenser inlet sends liquid back evaporar outlet Key point Evap. out SH comp. out SH Fig. 12 Hot Gas Heater based on Accumular Cycle Fig. 14 New Accumular Cycle concept
Check valve Evaporar Orifice tube Operation changing valve Electromagnetic valve Differntial pressure valve Hot gas tank Oil return hole Fig. 15 Hot Gas Heater based on New Accumular Cycle [Ambient temp. : -2ºC Warm up 4km/h Diesel 2.21 Bolwer Hi] Temp. (ºC) Hot gas ON Hot gas OFF 6 4 Outlet air temp. +18ºC 2 Cabin temp. +9ºC -2 Evaporar outlet air temp. (Hot gas ON) 5 1 15 2 25 3 Time (min) Fig. 16 Heater performance
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